A PETROGLYPH RECORDING DEMONSTRATION
PROJECT

for

Petroglyph National Monument
Albuquerque, NM
October, 1994

prepared by

Henry Walt
John Brayer
July 1994

TABLE OF CONTENTS

INTRODUCTION........................................................................................3

I. SURVEY OF CURRENT TRENDS IN PETROGLYPH RESEARCH...............4

II. SURVEY OF IMAGE RECORDING TECHNOLOGIES..............................9

III. NON-IMAGE DATA RECORDING TECHNIQUES AND OPTIONS........20

IV. COMPUTER IMAGING AND DATABASE SYSTEMS............................26

V. HISTORY OF THE PILOT PROJECT......................................................39

VI. DEMONSTRATIONS...........................................................................48

VII. SUGGESTED DEMONSTRATIONS.....................................................51

VIII. COST ESTIMATES..............................................................................53

IX. RECOMMMENDATIONS & CONCLUSIONS.......................................55

REFERENCES..............................................................................................57

INTRODUCTION

Issues with and questions about the recording of rock art are becoming increasingly important as interest in the subject grows and becomes steadily more multidisciplinary. With attention on the rise, more sites are being identified and recorded. For this reason, there is a need for a certain degree of standardization in rock art recording procedures. Federal and state agencies often have multiple rock art sites to oversee, scholars require systematic data to analyze, and need data with intersite compatibility for comparative study. Our demonstration project will attempt to address and assess previous and current recording procedures, as well as a broad range of applicable technologies, both tried and true, and new and untested.

This project evolved from the National Park Service's interest in protecting and interpreting the monument's resources. The rock art at Petroglyph National Monument has not been comprehensively or systematically recorded. Yet these fragile glyphs are increasingly threatened by their proximity to metropolitan Albuquerque and the encroachment of this city's growing suburbs.

The Park Service's contract with Walt and Brayer is a prelude to the full-scale recording of the Monument's resources. The intention of this pilot project is to survey current trends in rock art research, to assess current data recording procedures, and to create an automated demonstration of imaging software. Specifically, these tasks include the assessment of current trends among rock art scholars, the evaluation of applicable automated technologies, and the development of field recording methods for the Monument that are also appropriate to other rock art sites and settings.

This report is organized into 8 sections. First is a review of the current status of rock art recording with particular emphasis on petroglyphs. The subject of the section two is the recording of rock art images, and specifically the field recording of image data. The recording of non-image data is the subject of chapter three. Processing and storage of images is discussed in section four. This includes computer systems for recording, processing and for database storage and retrieval (both hardware and software). Section four deals with both image and non-image data processing. Section five reviews the history of the pilot project from which these results were derived and describes the computer demonstrations. Cost estimates are projected in chapter seven. Finally, section eight contains our conclusions and recommendations.

I. SURVEY OF CURRENT TRENDS IN PETROGLYPH RESEARCH

One of the primary objectives of our current trends survey has been to gather as much information as possible about prevailing and accepted recording methods and protocols. We felt that the most direct and timely way to acquire this information was to communicate with people who have had extensive experience in recording petroglyphs and pictographs. For this, we assembled a list of questions, topics, and issues. Our questions were focused specifically on field recording issues, technological options, and automated databases. This inquiry quickly evolved into a standard questionnaire. What we found as a result of our study was, in fact, that there were no prevailing and accepted protocols. Scholars, managers, and institutions each have their own field methods and accepted recording procedures and there has been little or no effort to standardize the recording of rock art. Although some conventions have crept into the recording process over the years, many such tried and true methods are now outmoded due to advances in newly available technologies.

Our first interviews began with local scholars and enthusiasts. These included Jay and Helen Crotty and Jerry Brody. The Crotty's experience with large-scale recording projects, including the Three Rivers site, was extremely valuable during the early stages of this project. We also discussed our concerns with several BLM archaeologists and managers in New Mexico and Arizona as well as other federal and state managers in the region. During these early stages, we adhered closely to our questionnaire and initial concerns about recording and automation. But, as we absorbed information through our interviews and other project activities, the interview process matured and became more open-ended.

The next set of interviews were conducted by phone with scholars primarily in California. These included David Whitley, William Hyder, and Dan McCarthy. By this time we began to realize that there was only a limited amount of information that could be gathered by these means and that nobody had the answers we were looking for. No one has expressed more than a modicum of satisfaction with the results of large-scale or management oriented recording procedures. Information gathered for such projects continues to be virtually inaccessible, remaining in shoe-boxes and as original field forms. David Whitley has accumulated information from a large number of petroglyphs in the Coso Range, but this data is broad and elementary. For instance, he discusses the number of sheep portrayed, but not their variation or context. Smaller, research-specific recording projects have been far more successful to this point. This is, of course, not surprising. Scholars with specific and well-defined interests have no problem in pinpointing attributes necessary for their research. It is also much easier to handle and manipulate smaller sets of data. In most cases, large-scale recording programs have only ill-defined management concerns for guidance and structure, with little input from interested scholars or knowledgeable cultural descendants. In addition, management concerns may be limited to simple inventories that do not open or expose the data to further manipulation or research.

Following our interview in the Western United States, we began to correspond with scholars in Australia and South Africa. We chose likely correspondents from articles and books that interested us. Our contacts included David LewisWilliams from South Africa, and Andr้e Rosenfeld, Clifford Ogleby, Bruno David, David Lambert and Graeme Ward from Australia. Although we presented these people with the same questionnaire, we also included a long cover letter which addressed our concerns and interests at that stage of the project. Our response from the overseas scholars was thorough and prompt. All offered to assist us in the future if needed, and all expressed a strong interest in our objectives.

The following is a summary of relevant responses from our interviews:

Questionnaire

  1. For our records we would like to know the type of rock art sites you've documented and the number. (variable entry here depending on correspondents research interests). Have your recording techniques differed dramatically by site or by research objective - or have you found a level of consistency to be useful or necessary between sites for comparative purposes. • A full range of site types have been recorded by our correspondents. These include large and small drawing, stencil, painting and engraving sites on exposed rock, overhangs and caves, etc. No one seems to have developed a consistent inter-site format, although several respondents consider this important. Virtually everyone admitted to a great deal of recording variations between sites. The Crotty's have mapped sites differently, depending on terrain, but these differences are not critical and can be accommodated for in the postfield manipulation of the data. Bruno David feels that a level of consistency is necessary to make certain kinds of information available. Surprisingly, no one discussed inter-site information as a necessity for research. • There is a consensus that field recording is time-consuming, especially if drawings are required. New technology may shorten field time somewhat, but the effort and time necessary to record rock art properly must be factored into any project.
    • Most scholars frowned upon the recording of rock art without a research design, but also acknowledge the importance of recording in and of itself. Management-generated recording projects traditionally paper over such issues by developing vaguely watered-down research designs. The solution to this is to consider the management of rock art an end in itself, if certain considerations are kept in mind. First, much of what has previously passed for rock art recording has very limited use due to a lack of rigor and forthought during this process. Images cannot be relocated without a great deal of effort, the most rudimentary data is difficult to access without automation, photographs are inadequate, drawings lack scale, and field notes appear to be only loosely organized, etc. If data is recorded and organized so that images can be relocated, associated with neighboring images, easily accessed and updated, many research options will become possible. A thorough recording process such as this would easily and naturally lend itself to research and a more intense examination if this was also a requirement. That is not to say that further field recording would be unnecessary in every instance. It is impossible to meet the needs of all future research, and unreasonable to assume that such goals can be met by any recording system. However, a thorough and rigorous recording format can serve as a gateway for those interested in research, making information accessible rather than inhibiting and confusing higher levels of analyses.
  2. How do you store images?
    1. photographic prints
    2. slides
    3. automated data base • In the United States, images are kept as black/white prints for archival reasons. In Australia, people we contacted utilized a number of media, black/white photographs, color slides, and a limited use of automation. The digitization of images eliminates the need for black and white photography as an archival requirement.
  3. We feel that documenting the relational context of images is critical to the successful recording process. We know of several rather time-consuming methods to accomplish this, but nothing quick and elegant. Has this been a concern of yours and if so how have you handled it? • Everyone agreed this is a problem, but there were few viable solutions offered. Clifford Ogleby (University of Melbourne) feels photgrammetry is the answer, although Bruno David (University of Queensland) has also used this technique and feels the results do not warrant the time necessary. Others with limited experience in photogrammetry also felt it was overly time consuming. Bruno David and Andr้e Rosenfeld use scale drawings to illustrate contextual associations.
  4. How do you record the location of images and panels? Do you use GPS? • Some Australians use GPS regularly. Ogleby uses GPS to locate the site, photogrammetry to orient images within the site, and electronic theodolites to coordinate other points on the rock surface. Archeologists in the United States are beginning to use GPS to record rock art since this is becoming a standard technology for government-contracted archeological surveys.
  5. Do you use standardized photographic methods? • There was not much feedback on this point. Most people use the same film speed, film type, etc. There was a complaint raised concerning the slow turn-around time of the photographic process (Brody). This problem is eliminated if digital cameras are used.
  6. Do you use a computerized database? Which one? • No databases are utilized regularly, although some projects in Australia have incorporated GIS into regions that include rock art sites. At least two state agencies in Australia, the News South Wales National Parks and Wildlife Services and the Australian Institute for Aboriginal and Torres Island Studies, sporadically use a database called 'Minarch'.
  7. When photographing pictographs do you use any type of color correction or geometric [angle of camera to rock surface] correction? • There is some, intermittent use of color correction with the inclusion of standard color charts in photographs, but no geometric correction whatsoever other than eyeballing the average plane of a rock surface.
  8. Are you interested in any of the following technologies?
    1. 3-D elevations [including virtual reality]. An elegant way to record is to recreate the landscape on which images are found and then record the images. There are a number of ways to document a three-dimensional space in the field. Among these are stereophotography, structured lighting, and laser rangefinding. • Everyone loved this concept. The Australian's experiments with photogrammetric plots have drawn mixed results and opinions. However, all respondents were fond of the notion of 3-D elevations.
    2. Have you used any techniques to date petroglyphs or pictographs? • Dating is becoming increasingly important to anyone doing serious research. The problem remains the reliability of dating techniques (discussed elsewhere in this report).
    3. Image searching - in its final form, our database will incorporate some method of image searching, using the digitized image itself to search for other similar images.
      • We're not sure if everyone understood this notion. We are proposing a searching procedure that bypasses coded information and relies solely on pattern recognition and digitized imagery. Unfortunately, our above description was unnecessarily cryptic and lacking in clarity. However, everyone felt that this is a very attractive concept and worth pursuing whether they fully understood it or not.

All respondents expressed interest in our technological options and agreed that conformity, digitization and automation are necessary for the advancement of the field. However, of the correspondents only Clifford Ogleby has had extensive exposure to a wide variety of digitized and automated technologies, perhaps due to the fact that he is a geographer.

Although the respondents varied widely in their understanding of and exposure to the many new technologies we are considering, they shared a concern for the development of rock art research as a subdiscipline. All felt that a greater rigor is necessary, greater inter-site compatibility is a must, and that the recording procedures we are exploring may well aid in the maturing of this process. Our long-distance interviews have not ceased, but are on-going as one aspect of our continued interest in rock art.

At this time, we believe it is not fruitful to concentrate on this survey process, at least in the form of further mailings of questionnaires. We believe we have contacted a large and representable sample of scholars and managers and have found that they have little knowledge of or experience with the kinds of technology we are proposing. Further, we do not believe that computerized recording and database storage of rock art is being used by any major project anywhere in the world. Although this technology is not new to other archaeological subdisciplines, it does not seem to have found a home among rock art scholars. We have also examined a number of rock art recording manuals. These documents span a wide range of settings and media, but do not incorporate current available technologies or procedures for standardization. We therefore feel it necessary to develop our own procedures and recording formats, perhaps leading toward standardized protocols if successful.

II. A SURVEY OF IMAGE RECORDING TECHNOLOGIES

This section reviews techniques only for IMAGE recording and covers only initial field techniques. The recording of non-image data and the rerecording or digitization of drawings are covered later. Image and other data storage is also discussed below.

Image recording can be divided into manual and automated methods, depending on whether or not an image sensor is used. Manual techniques include drawing, tracing, computer aided drawing, rubbing and casting. Automated techniques use some form of sensor, scanner or machine to capture the entire image. The most frequently employed automated technique is photography. Some of the criteria used to evaluate these technologies include image completeness, accuracy and efficiency. By image completeness, we mean recording all properties of the object even when the glyph is very faint or difficult to decipher.

  1. Manual Recording
  2. Drawing

Drawing has been one of the preferred rock art recording techniques for many years. It has the advantage of being inexpensive and requiring little extra equipment. It also allows the recorder to use his/her interpretation to fill in details that are very faint in the original. This, of course, presents both positive and negative problems and consequences. That is, the subjectivity of interpretive conventions can become a serious disadvantage. Faintness and superposition are common problems in rock art that are perhaps best overcome by drawing and tracing techniques. Sketching or drafting is likely to be inaccurate if methods are not tightly regulated. Drawing also has the disadvantage of requiring substantially more time and skill by the recorder than does photography. Drawing is faster than tracing but less accurate. Sketches or drawings have another advantage over tracings in that they avoid rock contact.

To be of use, drawings must be rendered to scale and incorporate a consistent set of visual conventions such as the use of solid lines, dashed lines, stippling and cross-hatching. Since drawing is most useful for marginal glyphs, it is important to check sketches and rock surfaces under various lighting conditions. Field kits should contain regular drawing paper, graph paper, erasers, pencil sharpeners, colored pencils, pencils of assorted hardness , and mechanical pencils. Field drawings should be inked at a later time and then checked against the original. A drawing can be one of 3 types, each successively more time consuming: a field sketch, a ruled drawing and a grid drawing. A sketch is rendered unaided. A ruled drawing uses a flexible ruler to measure key features and is done on graph paper. A grid drawing makes use of a string grid over the original to produce accurate scale and composition.

We would expect drawings to be used rarely for recording petroglyphs except in special circumstances such as when the glyphs are very faint, or partially obliterated. In many of these cases, computer aided drawing can be more reliable. Drawings should be rendered as a matter of course for 'panel complex' and 'unit' maps.

The following convention sets are compiled from various rock art recording manuals [2:Texas]

Glyph Drawings:

  1. Take a position perpendicular to the glyph center.
  2. Put a north on a plan view or up arrow on an elevation view drawing.
  3. Label the sketch. (glyph no., panel no., site no., date, time, location, artist)
  4. Draw the art.
  5. Recheck the labels.

Panel Drawings:

  1. Drawings should be dark and on graph paper so that they can be photocopied.
  2. An appropriate scale should be selected and recorded on the drawing. "Up" or "North" should also be designated. Site, unit and panel designations should be recorded along with the date, the location and the artists name.
  3. Key points on the object should be plotted on the drawing. Aids such as a string grid placed over the object or a ruled string around the perimeter should be considered.
  4. Avoid all extrapolation or interpretation of the image, recording only exactly what is present, including deviations and interruptions in lines due to deterioration.
  5. Overlays may be used to record graffiti or rock surface condition within the composition.
  6. Annotate the drawing with notes about cracks in the rock, rock surface features, scratches, etc.

Panel Complex:

  1. Show the related panels in their context.
  2. Use plan views as well as elevation or face views.
  3. A face view should be completed from a position perpendicular to the center of the face.

Site Drawings:

  1. Work in a team of 2 or more.
  2. Choose and label one or more datum points and then plot them on the drawing.
  3. Highlight the panels containing glyphs.
  4. Include at least an approximate scale.
  5. Tracing

Tracing requires more time than drawing, but produces a more accurate result with less skill. Mylar, drafting film, prepared acetate, or paper may be taped over the glyph or panel. Care should be exercised to never place tape over any rock art. Another tracing method involves the use of rice paper soaked in water and rolled onto a rock with a sponge roller. Tracings can also be made on transparent plastic film such as polythene, initially rendered in dark felt-tipped pen, then copied with India ink. The result of a tracing is durable and geometrically stable; such images can later be digitized and stored on a computer. Like drawing, tracing is time consuming and requires a certain degree of skill.

We would expect tracing to be used only when other methods are unsatisfactory for specific and limited areas.

3. Computer Aided Drawing

In addition to normal drawing, with modern digital equipment in the field, it is possible to use guided drawing. This concept begins with a digital photograph that is then printed lightly on paper. This printout can be accomplished in the field with a digital camera. The recorder can then return to the petroglyph and compare the image to the original glyph, making sketches of added areas or deleted areas in addition to other notations. Both the original image and the corrected drawing can be retained in the database for comparison and analysis.

This kind of drawing is a new technique and we cannot predict how useful it will be until we have field tested it. But it is likely this method will be very useful and used frequently. To annotate photographs with drawings will become a powerful recording technique.

4. Rubbing, Moulding & Casting

These methods require physical contact with the rock surface and may produce some damage to petroglyphs. Rubbings, moldings, and castings are also extremely time consuming. A traditional method of recording petroglyphs has been to make rubbings, using means similar to those for copying tombstones, other finished stone, as well as brass and copper engravings. Rubbings are not geometrically accurate. Further, rubbings with muslin and cobbler's wax have been shown to affect cation-ratio dating.

It is not clear whether casts can safely be made of engravings on hard surfaces using elastomer silicones and polyesters. These cause no apparent damage to the rock substrate, and are quick and easy to apply, producing precise and resistant results [Bahn&Vertut]. However, we do not know if these methods interfere or affect rock art dating techniques. Although mouldings and castings can be an extremely accurate way to reproduce petroglyphs, they present difficult storage problems.

B. Automated Recording

In this section, we have attempted to survey all possible automated image recording techniques. Our approach has been to consider all types of energy and all types of sensors capable of forming an image, rather than simply surveying those techniques that have already been used on rock art. In general imaging science, some techniques are used to reveal the internal structure of an object, some are used to record the object surface topography, and some are used to enhance the object contrast against its background. We discuss briefly whether these techniques have been used successfully on rock art.

There are fundamentally two modes of automatically recording physical phenomena. First there are active systems in which the object of interest is specially illuminated by some type of energy and the reflected, transmitted or scattered energy is measured. Examples of this are x-ray, ultrasound and radar images. Second are passive systems that utilize an objects own emitted or reflected energy, gathered from ambient illumination or environmental influences. This energy is then recorded. Examples of this are infra-red photography, scintogram photography, and normal photography. Although normal photography with the aid of flash might be considered an active recording technique, for simplicity we will consider it passive. The following is a review of active and passive recording techniques and their applicability to the recording of petroglyphs encountered at the Monument. Since standard photography is so important it is discussed in a separate section.

  1. Active Recording
  2. Ultrasound (Internal Structure)

This method illuminates the object with acoustic energy at a frequency above the range of human audibility. The sound waves propagate into the object and are reflected off density transition surfaces within the object. The reflected waves are then collected and displayed by the same piezoelectric sensor that generated the initial wave. The resulting image is a display of a 2D plane with one transverse dimension and one dimension representing depth of penetration, i.e. a plane penetrating the object. The most common application of ultrasound is the prenatal viewing of babies.

Because petroglyphs are surface features and since ultrasound may in fact damage the rock substrate, ultrasound does not appear to be a good candidate for rock art imaging. We found no literature on the use of ultrasound to record rock art.

b. X-ray (Internal Structure)

This method illuminates the object with electromagnetic x-ray radiation and then typically records the transmitted or scattered energy. The most familiar application for x-ray is medical and dental.

X-ray is most useful in it's ability to display internal features of objects that are otherwise opaque to visible light. Since petroglyphs are a surface feature, x-rays are unlikely to be useful. We found no literature on the use of x-rays to record rock art.
X-rays might reveal the internal structure of a layered pictograph.

c. Flourescence Photography (Image Contrast)

Flourescence photography employs a generator-powered xenon electronic flash that produces ultraviolet light at night. Special filters are used on the flash and on the camera lens. Kodak Ektachrome 6117 film is commonly used to capture flourescent images. Flourescence has been used to record rock art paintings where organic or mineral paints and dyes have contained compounds that fluoresce. It is unlikely but unknown if there is a fluorescing mechanism that would enhance the contrast in petroglyph images.

d. Laser and Radar Ranging (Object Topography)

In laser and radar ranging an electromagnetic pulse is emitted from an antenna and travels to the object surface. The pulse reflects off the surface and returns to the antenna where the time of flight is measured to calculate the distance from the antenna or laser focal point to the object. As the beam is scanned over the object surface, a profile of the object surface elevation is produced. From this data an image can be constructed with image brightness proportional to surface elevation. A contour map of the surface can also be produced by this method. Using a coherent laser and more complicated imaging, a hologram of the object can be constructed.

This technology may have application in the recording of detailed panel complex topography or detailed rock surface topography. Such information may be of specialized interest; and, therefore, a secondary priority. We found no reference to the application of this technology to rock art recording.

e. Structured Lighting (Object Topography)

Structured lighting is the projection of a known geometric pattern such as a grid or a series of parallel lines onto the surface of an object so that threedimensional information can be extracted from the resulting photograph. This is essentially a cheaper way to get information similar to but less accurate than that provided by laser ranging. This technique has been used extensively in manufacturing production line quality control applications, in the Martian Lander science platform, and may also be useful in the recording of petroglyph rock surface topography. Similar information can also be obtained by stereo photogrammetry, which can be accurate but is very time consuming.

2. Passive Recording

  1. Ultra-violet (Contrast Enhancement)

In ultraviolet photography, the film is exposed by ultraviolet wavelengths only, either as a component of natural light or as emitted by an artificial source. This film requires the use of specific lenses designed for U-V light as well as special filters such as the Kodak Wratten 18A filter. Ultraviolet film is also necessary. The resulting photo is black and white. Few examples of the usefulness of U-V photography exist in the literature and those are restricted to very faded, painted images.

b. Infra-Red Film (Contrast Enhancement)

Infra-red photography has been found to be useful in examining painted images and especially in examining under drawings. The technique requires only conventional photographic equipment and illumination from conventional incandescent lamps. Focus corrections for the longer wavelengths and special infrared film are required. This technique has also been reported to be helpful for petroglyphs photographed in direct sunlight. This is due to the increased contrast caused by the greater absorption of darker patina in the infrared band. The result of an infrared film is a black and white image.

c. Chalking Before Photography (Contrast Enhancement)

What was once an acceptable method of enhancing shallow and patinated images is now frowned upon for several reasons. The chalk interferes with dating techniques, rendering any chalked petroglyph undatable. Chalking may also distort and alter an image if the utmost care is not taken. Either way, chalking is no longer an accepted recording option.

d. Surface Wetting (Contrast Enhancement)

Contrast and color saturation of the image may be improved by wetting the surface of the rock prior to photography. In general, wetting (of petroglyphs, not pictographs) by distilled water cannot be regarded as harmful since most rock surfaces other than those in overhangs or caves are continually exposed to natural elements anyway.

3. Standard Photography

  1. Camera & Camera Stability

The most popular and cost effective photographic format is the 35mm singlelens reflex using black-and-white or color print film. The 35mm camera is by far the most popular and widely-used format today. Enlargements from 35mm film generally retain their resolution up to a size of130x180mm (about 1/4 of an 8x10 or about 5x7). It's popularity affords countless options in lenses, filters, auto-manual formats, and peripherals. Larger format cameras offer greater clarity and detail, but the cost of developing and printing large negatives is prohibitive. Color print film has gained tremendously in popularity over the last few years because of quick turn-around times for printing and some lowering of prices.

In past years, petroglyphs were primarily recorded on black-and-white film because of archival considerations. Any recording process now envisioned will involve conversion to a digital format at some point in the process, thus eliminating concerns over the archival properties of color. Color imagery offers a far greater range of visual information and greatly increases the likelihood of successfully recording data by photographic means. It is probably a good idea to employ some form of flash for all petroglyph photography. A flash or set of flashes eliminates the need for tripods or other means necessary to ensure camera stability in low light situations.

b. Orientation

The camera should always be oriented so that the film plane parallels the rock surface as closely as possible. An "Up" arrow should designate the vertical direction in the image. If possible some indication of the surface perpendicular and sun or other illumination angle should be included. All of this can be accomplished by having a small surface perpendicular attached to the rock surface and include it in the photograph. The shadow of the perpendicular will indicate the sun conditions and direction, and length of the perpendicular will indicate the relationship of the camera optical axis to the surface perpendicular.

c. Flash & Other Artificial Illumination

Light to medium overcast conditions are the best illumination for natural lighting. On bright, clear days the very high contrast between directly lit surfaces and deep shadow causes great difficulty. Most photographs taken under these conditions that lack extra precautions are very poor in quality. For color photography, lighting conditions in early morning or late afternoon seem to produce softer surfaces, but the color temperature of these lighting conditions is often less than adequate.

One way of overcoming the limitations of natural lighting is to use portable electronic flash while shading the subject. In addition to producing very controllable lighting conditions, the very short flash durations virtually eliminate any lack of sharpness due to camera movement.

Some rock art photographers have been successful in using portable reflectors to enhance the light falling in shaded areas.

A common photo technique for petroglyphs is to use raking artificial light at night. This enhances any surface irregularities that otherwise would be difficult to capture. The idea being that side lighting causes shadows to form in the grooves, thus increasing contrast by making the grooves darker. There is, however, the potential to distort the image with low-angle lighting. This can be partially overcome by lighting the image from more than one direction. In fact, it is best to use raking light from several directions, with several exposures to show the relief from each angle. It is also probably necessary to have a steady light source to experiment with various angles for the best shadowing. An angle of about 15 - 30 degrees between the object plan and the incident light rays is best in most cases. We do not expect the technique of raking light to be as successful at Petroglyph National Monument for several reasons. First, the petroglyphs in the Monument have lighter grooves than the background, so shadows in the grooves would tend to decrease the contrast. Second, the rock texture is very coarse so that shadows created by the lighting would be highly irregular. Third, the very large number of petroglyphs and the rough terrain rule out the use of night photography on a large scale for practical reasons.

d. Polarizing Filters

When photographing rock in direct or light haze natural light, specular reflection of the illumination off the rock surface causes a glare which can obliterate the petroglyph image. On most days in the Southwest this is a serious problem. Polarizing filters are extremely useful at certain sun angles. Polarization significantly reduces but does not eliminate the specular reflection while only slightly reducing the amount of subject reflection. The usefulness of the polarizing filter is extremely angle-dependent and frequently is not sufficient to reduce glare to acceptable levels. In such cases, shading of the subject and the use of diffuse reflected illumination or flash is mandatory.

e. Other Filters

Various filters have been shown to be effective in enhancing contrast in black and white photography. Various other filters are necessary for specialized applications such as infra-red and ultraviolet. For color photography the only filter to prove frequently useful is the polarizing filter discussed above. It is unlikely that other "colored" filters will prove useful, and in any case digital image processing can probably produce the same effect.

f. Black and White Film

For many years black and white photography has been the standard of recording for archival purposes because of its long-term image stability. There are many types of film that are adequate and most have been used successfully.

g. Color Film

Because most images of petroglyphs in the future are likely to be digitized and stored archivally in digital form, film permanence is no longer a major consideration. However, among color films, Kodakchrome has the best long term stability, lasting well for over 10 years. Whatever film is used should match the color temperature of the intended illumination. The film should also have fine grain and render colors well. A standard color target should be used in all images. Digital color and contrast correction can correct any imperfections in the film later in the process. However, image digitization is unlikely to take advantage of full film resolution.

h. Film Roll and Photo Numbering

It is important to have a convention for the numbering of photos. Film canisters should also be labeled before the roll is shot. The first exposure of any roll should be of a chalkboard containing date, photographer, site, unit, photo numbers, etc. Immediately upon return of processed film, photos should be numbered and labeled. While in the field, a photo log with photo data sheets should be filled out as exposures are taken.

i. Exposures

Generally, modern 35 mm and digital cameras have adequate internal exposure meters so that multiple exposures are usually unnecessary. Occasionally these meters are fooled by lighting conditions (especially in bright sun and deep shadow and other strong contrast conditions). If using a digital camera, the exposure can be checked on a laptop computer in the field, eliminating the need for exposure bracketing. One exposure should be taken with the color target, up arrow, surface perpendicular, glyph number, panel number, date, photographer and metric scale bar. Further exposures (bracketing exposures) should be taken from the exact same camera angle and position without any extra equipment in the image.

j. Photo Storage

All photographic materials are sensitive to heat and exposure to strong light. Film should be kept in a cool (or at least not hot), dry and dark place. Separate copies of archival photos should be kept in separate locations for backup.

k. Photo mug-board

Each photo should contain:
A color scale
A metric scale
An up arrow
A surface perpendicular
panel number
glyph number
date and time

l. Photo Log

The photo log includes: site number, location, date, type of film, film roll number, ASA, size of roll, exposure number, subject, panel number, time of day, light conditions, direction of camera, direction of subject, and comments.

m. Camera maintenance

The lens should be dusted frequently. Cameras used in the field must be periodically cleaned because of the added exposure to dust, wind, rain, etc.

C. Types of Images Recorded

The following is a list of potential photographic subjects to be recorded at Petroglyph Monument:

  1. Glyph

In the recording format we have developed, a glyph is a single image, isolated either iconographically or physically from other petroglyphs. Such an image should be recorded with good spatial resolution, color fidelity and geometric accuracy. Every effort should be made to have the camera on a parallel plane with the glyph. A scale, panel perpendicular, image-up-arrow and color target should be present in all such photographs. A glyph datum is established as a matter of course during the recording process.

2. Panel

A panel is a single, mostly flat surface on which there are one or more glyphs. A panel photograph records a single planar surface containing from one to several petroglyphs. This photograph type must always contain a scale, panel perpendicular, image-up-arrow and a color target. Camera lens and panel surface should be parallel. A panel datum must always be established.

3. Panel Complex

A panel complex is a group of subject related or geographically related panels. The purpose of a panel complex photograph is to illustrate the interrelationship of panels that make up the panel complex. Because of the many ways panels can be joined, there is no set format for this type of photograph. In all panel complex photographs, the camera location and optical axis direction should be established on a Unit map. A panel complex datum is always necessary.

4. Unit

A unit is a subarea of convenient recording size for research or administration. A unit photograph shows the general topography and layout of the unit. Each corner of a unit can be considered a datum point.

5. View

A view photograph reveals an aspect of the landscape from a locality containing a significant set of petroglyphs. In all view photographs, the camera location and optical axis direction should be established on a Unit map.

6. Aerial

An aerial photograph reveals the layout of an area containing many petroglyphs. It potentially provides a map interrelating a number of petroglyph units.

III. NON-IMAGE DATA RECORDING TECHNIQUES AND OPTIONS

This section will address the recording of non-image data. This includes location, date, orientation and other types of contextual, identifying, and evaluative information. This type of data will usually but not always be associated with an image. This information is best understood in an hierarchical sequence of sites, units, panel complexes, panels and individual glyphs.

It is traditional to have recording forms for each level of data. Later, this information is summarized and reorganized in reports or publications. Original recording forms are then stored in a suitable archive. In such an archival setting, recording forms are of limited value because they are difficult to search, access and analyze.

In recent years, a small number of scholars have entered their rock art data into a computerized database for easier access. In general, these databases have been quite successful, although relevant information is still frequently not as accessible as it could be. In addition, the extra step of entering data into the database is quite time consuming.

The most efficient recording method is to enter the data while in the field directly into the computer. This eliminates an extra data entry step and makes information immediately accessible. The data can be made more accessible by using a standard database and by eventually making such information available through the Internet.

A. MAPS

Maps serve several important functions during and after the recording process. Prior to field time, maps are indispensable in planning strategies and defining units of analysis. Units of study can be selected either from easily identifiable geographic features, known glyph clusters, or measured sectors. Second, accurate unit maps serve as a means of field checking locational information being recorded by other means. The location of glyphs and their relocation by scholars and managers are another primary function of maps. Finally, it is important to have accurate locations as part of the database so that glyph distribution can be analyzed and understood relative to landforms and natural features.

The complete recording process results in two types of maps, locational and site-descriptive. More detailed site-descriptive maps contain intra-site information that contextualizes individual glyph locations.

Increasing use of Geographic Information Systems has led to a growing need for accurate digital map information. The following is a review of the kinds of digital map information that are readily available.

GIS information usually begins with digital terrain elevation data. There are several sources for this data.

The Defense Mapping Agency produces an elevation product called "Digital Terrain Elevation Data" (DTED). It is available in two levels, DTED-1 which has 100 meter resolution and DTED-2 which has 30 meter resolution. Coverage of DTED-2 is limited.

The US Geological Survey produces products called "Digital Elevation Models" (DEM). There are 2 types, 1-Degree DEM and 7.5 Minute DEM. 1-Degree DEM is like DTED-1. Each 1-degree block costs $75. 7.5 Minute DEM has resolution of 30 meters, 7.5 minute map costs $90 for an access fee and $7 for each block (coverage is limited).

Private companies can produce this data from aerial photography but the cost is much higher. The actual resolution achievable is dependent on the resolution of the aerial photography and the quality of the ground control points (known fixed positions) that can be provided. Generally a production period of 3 to 4 months and a cost of at least $2,000 - $5,000 is needed for an area the size of a 7.5 minute map.

B. LOCATIONS

The following is a brief review of several traditional as well as newer, experimental surveying techniques. Also critiqued are methods of producing accurate locational information. Again, the emphasis in this section is on field recording and the creation of field maps. A later section will discuss the processing of location information into a GIS or image database and the subsequent construction of petroglyph resource maps.

At this point it may be best to approach locational information and the locating of petroglyphs through a combination of traditional techniques and the quickly developing electronic, GPS and GIS technologies. Traditional recording procedures for archaeologists include the use of USGS maps, UTM coordinates, township and range designations, as well as the use of compasses and transits for determining angles and elevations. If the terrain being mapped has enough elevation gain, locations are relatively easy to pinpoint by such means.

We have attempted several traditional surveying techniques during our pilot study and found them generally to give adequate accuracy although they are prone to error. The most important limitation of such techniques is their timeconsuming inefficiency.

At present, there seem to be three viable methods for locating glyphs and recording this information.

  1. Trilateration with a hand-held laser distance meter

A hand-held laser distance meter such as the Leica "Disto" can measure distances to a target up to 100 meters away within 3 mm. To use this instrument, target boards are set up at each of the 4 corners of the study unit. By measuring the distance to the 4 corners from the glyph, the position of the glyph can be fixed and checked. The measurements are manually entered into the computer in the field and later calculations fix the position. These units are lightweight, rugged and inexpensive ($1500.). One person in the recording team can make the measurements and enter the data in under 2 minutes. Built-in NiCd batteries have to be recharged after approximately 400 measurements. The method would require that the corners where the targets are placed be known fixed positions, surveyed by conventional methods or by GPS.

Advantages:
Inexpensive equipment
Single operator
Some self-checking
Adequate accuracy

Disadvantages:
Possibly error-prone
Possible difficulties in bright sunlight Essentially a planimetric measurement Possibly unsafe laser light

2. Radiation with a surveyors total station

This technique requires an electronic surveying station to be set over a known fixed point at the base of the unit to be recorded. An operator stays at this station to make measurements and enter data. A second operator must stand at the glyph with a prism pole. The survey station can measure and even automatically record the bearing, elevation and distance to the glyph from the fixed point. The station measures the bearing and the elevation angles by sighting on the prism. Distance is measured by an infrared laser beam from the station to the prism and reflected back to the station. An electronic total station is small but must be mounted on a large tripod. The total package is bulky and heavy. NiCd batteries for these stations must be recharged daily. The prism pole is relatively lightweight and portable. The cost of this equipment is probably about $10,000.

Advantages:
Some self-checking
Best accuracy
Essentially a 3-D measurement
Only need fixed points at base of unit

Disadvantages:
Expensive equipment
Two operators
Possibly error-prone
Bulky total station

3. GPS

GPS is a developing and popular technology, with a growing presence among archeologists and scholars recording rock art [4]. At its present state of accuracy, GPS is best suited for establishing control point datums from which other locations, including glyphs, are derived. Standard surveying techniques or other means must then be used to obtain local ground coordinates for rock art imagery.

The least expensive Global Positioning System Units, such as those used in the pilot study, are able to record the position of petroglyphs or other points to an accuracy of only about 2 to 5 meters. In areas where petroglyphs are densely packed this is inadequate. But many of the petroglyphs at the Monument, as elsewhere in the Southwest, are sparsely strung out over many miles. In settings such as this, these inexpensive GPS units are a practical way of acquiring reliable positioning data.

At minimum, 'Unit' corners can be located and recorded with GPS field units. When employing this method, panel complexes, panels, and glyphs are manually measured and placed within the unit boundaries. We attempted to locate panel complexes with the GPS units but found the margin of error unacceptably large for this purpose. Extremely important in our recording process is the precise location and association of panels and glyphs. The GPS technology and hardware we sampled did not support the precision we require.

However, GPS technology is changing and improving swiftly to a point where slightly more expensive GPS units are now apparently able to locate individual panels and complexes within an accuracy of 1 meter. More accurate units can greatly simplify the contextual recording of rock art by eliminating the need for establishing datums and measuring from these to individual glyphs and panels, all very time consuming. To obtain an accuracy of less than 1 meter, differential correction is still necessary. This means averaging the recordings over a period of 2-3 minutes and a total measurement time of about 5 minutes per measure. These units are lightweight, rugged and portable with a cost of about $10,000. Only one person is required to accomplish the measurements. A nearby base station of equal quality is also necessary. Differential correction requires obtaining data from the base station and using system software to correct a set of points.

Advantages:

        Single operator
        Adequate accuracy
        3D measurement
        No need for separate set of surveyed points

Disadvantages:

        Expensive equipment
        No knowledge of coordinates in the field
        Dependence on base station measurements

C. RECORDING COMPLETENESS

Methods and procedures must be developed to assure that recording is complete. Completeness of recording for a particular field form can be enforced by the recording software if a laptop is used in the field. Another problem is to ensure that all glyphs are recorded. Quality control and sampling procedures can give an estimate of how many glyphs have been missed. Part of the development of any large-scale recording process should use such techniques to assure an acceptable estimated miss rate.

D. RECORDING CONSISTENCY

It is essential to maintain a level of consistency in field measurements and for the subjective judgments required to record rock art. This is particularly important in the classification of glyphs and their sorting into one of the predetermined categories. A consistent set of protocols and conventions must be adhered to in the field.

E. STYLE

Petroglyph 'styles' have been identified in the Southwest and elsewhere for many years. Such styles have been elucidated and utilized as temporal and cultural markers from the very beginnings of rock art recording. However, with the recent advent of directly dated petroglyphs, stylistic chronologies have not held up well elsewhere in the world. Therefore, any reference to petroglyph styles has not been included on our recording forms. Further, the ability to make ethnic or cultural identifications on the basis of petroglyph styles also remains speculative. And although some iconographic images in the Southwest are clearly historic such as engravings of horses or figures with guns, these are far and few between. Until the Monument's petroglyphs, or images elswhere of similar styles can be reliably dated, any style designations serve little purpose.

F. NATURAL ELEMENTS IN THE DESIGN

Often natural rock features such as cracks or projections are incorporated into an image. These include faces split and rendered on two adjacent surfaces, or holes utilized as eyes, etc. These should be recorded as a matter of protocol.

G. SIZE

The most convenient method for rough measurement remains the tape measure. A distance scale should be included on all photographs to ensure proportional correctness. Accuracies in the sub-centimeter range can be expected when utilizing digitally-derived measurements. For boulders or cliff faces, the largest values of height and width should be measured. When an element continues over more than one surface, both panels must be measured.

H. AZIMUTH

Azimuth can be measured to an accuracy of about 2-4 degrees with a standard magnetic compass. A typical rock panel undulates by about this amount so greater accuracy seems meaningless. Care must be taken to keep the compass several feet in distance from volcanic rocks because there may be sufficient iron content in them to cause compass errors of as much as 180 degrees.

I. INCLINATION

The angle of inclination of a rock surface can be adequately measured to an accuracy of 2 degrees with the inclinometer on a standard compass. Since the panel surface itself typically undulates by more than this amount, this accuracy is sufficient.

J. DATING

Ronald Dorn, the father of modern petroglyph dating techniques, has recently described all surface varnish methods as experimental (Nobbs & Dorn 1993). There are currently three applications used to date petroglyphs: acceleratorradiocarbon, cation-ratio, and the stratigraphic analysis of varnish layers. At this stage it remains preferable to use all three methods to obtain minimum petroglyph ages. AMS radiocarbon dating takes advantage of the small amounts of carbon found in varnish. The problem with radiocarbon is isolating enough organic matter from the time of the petroglyph's origin and not from other varnish layers. New collecting techniques developed by Dorn may have overcome this problem to some degree (Nobbs & Dorn 1993). Cation-ratio dating assigns a relative date to varnish by measuring the ratio of cations (positive ions) of potassium+calcium/titanium which decrease with age. The problem with this technique is that chemical changes are influenced by variables other than time. The stratigraphic analysis of varnish is the third method, like cation-ratio, it is a relative dating technique. It must be executed in conjunction with cation-ratio and AMS radiocarbon to compare varnish layers in a microenvironment. This is done to see if varnish layering samples have been subject to similar environmental fluctuations. Dorn's current methodology employs all three methods because of their experimental nature, and this will remain the case until any one technique emerges as unquestionably reliable. Cation-ratio dating is by far the cheapest method, but it remains questionable if used alone. Radiocarbon dating is a good deal more expensive, but a necessary adjunct to cation-ratio at this point.

IV. COMPUTER IMAGING AND DATABASE SYSTEMS

In a major project such as the complete recording of Petroglyph Monument's glyph imagery, and in this modern high technology world, a computerized database system is really the only viable alternative. Computerized systems offer advantages in terms of accuracy, permanence, access and cost.

  1. Industry Standards

Before discussing the details of particular hardware and software systems, it is useful to understand the concept of an Open System. An open system is one which emphasizes system interoperability and data transfer at every stage of the design. For example:

In the anticipated recording of the Monument, there are many foreseeable uses of computing platforms. Below is a list of anticipated needs:

GPS Planning
GPS landmark and data file processing
GIS and Mapping
Image acquisition
Image display
Image output production
Image processing and manipulation
Image Database
Field Operations
Research record and bibliographic storage E-mail and research communication uses. Word-processing and paper and report preparation Budget and Project management

One of the key decisions to be made is the type of computing platform to be used. There appear to be three basic choices: Macintosh, PC (MS-DOS or Windows) or workstations such as a SUN with the UNIX operating system. There are also other options such as pen-based computers or specialized multimedia computers or turnkey image processing systems. For the anticipated project, with its emphasis on flexibility, it is unlikely these specialized systems will find much use. The following therefore, is a review of the 3 basic choices.

PC based systems with MS-DOS or MS Windows operating systems are the cheapest systems and generally have the most commercial software available. Recent improvements in the processing power of these systems mean that they compete very well in terms of processing power with more sophisticated UNIX workstations. PC systems are widely used and perhaps the most flexible type of platform. These systems are usually not as easy to use and especially not as easy to maintain as MAC systems. While the hardware processing power of these systems has improved, the operating systems are not as powerful as UNIX systems and are therefore, not as widely used for database and image processing research applications.

MACs are widely recognized as the easiest platforms to use and the quickest to learn. For that reason they are widely used by archeologists, and anthropologists. MAC applications tend to be very reliable and easy to learn. Prices of these systems are now competitive with PCs. Not as much application software is available for these systems as for PCs.

Of the three, UNIX systems are the most powerful and have the most flexible operating system. This is particularly true for graphics and image processing applications. UNIX is much more difficult to learn than either MACs or PCs, and very difficult to maintain. These systems are generally used by computer scientists and other types of computing researchers. UNIX systems are also the most expensive.

It seems clear that no one computer can satisfy all the needs of the project. Whichever platform or platforms are chosen, fieldwork would undoubtedly benefit significantly from the use of laptop computers for direct entry of data. This would eliminate a separate data-entry step.

  1. Image Capture
  2. Digital Camera

Digital camera technology eliminates the need for film and does away with a step in the process toward digitization. Images are captured in digital format and immediately ready for downloading to a suitable storage system. A major advantage is that the images can be previewed at the petroglyph site to determine if they are of good quality. This eliminates the need for a later return to the site to retake poor photographs. At present, digital cameras are quite expensive. Models with the resolution necessary for glyph recording are in the $10,000 range. This is the Kodak DCS2000 Digital Camera which is built into a Nikon 8008s 35mm camera body, has a resolution of 1524x1012, 24-bit, a disk capacity of 50 images and a SCSI interface. However, this cost will very likely drop in the near future. Another cost consideration of the digital format is the elimination of film, development, and printing costs which would be very high if photographing all of Petroglyph Monument.

b. Digitization

Image digitization can be accomplished in a number of ways. Digital cameras produce an image already recorded in digital format. Images can also be recorded on 35mm slides and then digitized utilizing specialized slide digitizers. Another option is to send images recorded on slides or negatives to Kodak where they are digitally transformed and placed on a compact disks. A further option is to take photographic negatives, make prints and digitize these on a desktop scanner. This is probably the most common technique for low volume applications. Scanners range in price from $100. to $1,000,000 depending on resolution, geometric and optical accuracy and speed. A typical desktop scanner for business document applications, which would be the cheapest type of practical value for this project might cost about $1500., would come with a SCSI interface and would be bundled with some image processing software.

Issues involved in selecting a scanner:

Image Quality
Resolution
Enhancement
Geometry
Consistency
Color
Usability
Ergonomics
Ease of Operation
Host Interface
Interface & Installability
Transport
Flatbed
Roller
Drum
Belt
Vacuum
Environment
Mixed documents
Background color
Skew characteristics
Jam removal
Dust buildup
Heat output
Noise
Safety
Electrical Noise
Functionality
Image rotation
Image de skewing
Image truncation
Resolution
Zone lift
Pixel inversion, color correction
Compression
Auto-Feeder
Reliability

c. Rerecording & Preservation of Existing Photography

In addition to digitizing new photography, it may also be necessary to digitize existing and historical photography. Although older photographs may be generally lower in quality and poorly documented, they provide an invaluable historical record of long term damage as well as other changes to the images. Existing prints can be scanned by a conventional desktop scanner or rephotographed by a digital camera. Slides must be scanned either by a special slide scanner or a digital camera.

2. Image Storage Technology

Random Access Memory

This remains a moving target and depends on the system architecture, operating system and application software. At present, something from 16-64 Megabytes is probably about right. This allows plenty for the system software and leaves enough for image panning. This means panning a possible 3000x4000 image, while also being able to flip through several pages of images.

Magnetic Disk

Again here things are changing. 1 Gigabyte should be considered a minimum. This would allow storage of 300-500 Megabytes of system software as well as use of a "working set" of about 50-500 images.

Magnetic Tape

This can be used for system and image database backup. Storage to and restoration from magnetic tape is very slow. Transfer rates are 100-200 kBytes/sec. More expensive systems transfer at 500 kBytes/sec. 8mm tapes store 5-100 Gigabytes. DATs store 4 Gigabytes Systems cost $2000.

CD-ROM Disk

Storage on optical media is 2 orders of magnitude denser than magnetic media, but it takes more than twice as long to access. CD-ROM drives are designed only to read data and are thus less expensive than WORM or erasable optical drives. CD-ROMs can be written by various commercial services. A standard CD-ROM is 120mm in diameter, stores 680 Megabytes and is removable. A typical access time is 200-300 millisec and a transfer rate is 300 kBytes/sec. Cost for a drive for a SCSI controller is $500. A changer for 15 disks can be $3000.

Optical Disk (WORM)

Writing on a WORM medium permanently alters the medium reflectivity so it cannot be erased. Some systems report 50 year data life. WORM drives are available in 300, 130 and 90mm diameters. 300mm WORM disks store about 5 Gigabytes. Access times are 100 millisec for 90mm to 600 millisec for 300mm disks. Transfer rates are 300-900 kBytes/sec. Systems cost from $10,000 for single systems to $100,000 for 10-disk changers with 3 sec access time.

Erasable Optical Disk

To write on an optical disk, a spot is first heated by a laser and a magnetic field is applied to reverse the magnetic polarity and thus the reflectivity. The spot can then be read by the same laser but with a non-heating power level. The information is erased the same way it is written. These systems can withstand several million cycles of erasure. The sizes, times and rates are similar to WORM drives. Prices start at $1000.

Jukeboxes

These are robotic disk changers that allow the use of several disk platters with a single read/write mechanism. These systems can get very complex, using access prediction and hierarchical caching to improve access times. Systems up to a terabyte can be purchased. The use of changers leads to the following terminology for storage:

On-line - immediately available. A permanently mounted disk

Near-line - available from a robotic mechanism in about10-20 seconds Off-line - accessible only by personal intervention.

Backup Procedures - For preserving system software For preserving images and the database
For preserving the system configuration from obsolescence.

Optical disks are relatively rugged. Tape backup using the traditional "grandfather, father, son" techniques is the least expensive. Duplication on a removable or separate disk is the least time consuming. The greatest long term threat to storage is system obsolescence. The storage media will probably last longer than the system on which it runs and when the system finally dies, the media may no longer be readable.

Factors in storage system evaluation:

Capacity

30,000 images x 1 Megabyte/image = 30 Gigabytes

Response Time (Mechanical+Seek+Transfer Factors) Cost
Permanence
Reliability

3. Image Displays

The most widely used type of display is the IBM VGA which has a resolution of 640x480 on a 14" screen for about 70 dots per inch (dpi). The most common refresh rate is 60 Hz non-interlaced. Most of these specifications are inadequate for image and document workstation applications. More reasonable is the XGA standard (1024x768) or better (1280x1024). Screen size should be at least 19" and if possible a higher refresh rate will reduce eye strain. Color display video cards typically use 8 bits-per-pixel to represent color. This is adequate for most graphics applications but is inadequate for true color applications. 12 bits-perpixel should be considered a minimum and 24-30 bits-per-pixel displays are more common for true color. Note that this is a lot of memory. A 30 bit-perpixel, 1000x1000 display requires (30x1000x1000)/8 = 4 Megabytes just for display. The video bandwidth for this kind of system must be 200-320Mhz. Other factors such as a non-glare screen and an adjustable base are also important.

Factors in Display Quality:

Resolution - number of addressable elements on the screen Image Stability - freedom from jitter and flicker Brightness & Contrast - a critical factor in fatigue Screen size - size together with resolution determines the dots-per-inch (dpi) of the screen.
Ergonomics - glare suppression and adjustability

4. Image Printing

Types:
Paper Printers
Dot Matrix - generally too slow, low quality. Laser Printers - the most commonly recommended type. Ink Jet Printers - intermediate between dot matrix and laser Light-Emitting Diode Printers - generally lower resolution than laser printers Thermal Transfer Printers - better quality than ink jet but slower. Paper Plotters - Generally intended for graphics applications. Poor for images. Film Recorders - Very expensive but very high quality photographic output.

B. Software

  1. Image Database Retrieval
  2. Geographic Information Systems

A Geographic Information System (GIS) is a set of software routines that are designed specifically for storing and displaying map information. Information or "map features" are generally stored in "layers" with each layer representing distinct information that can be superimposed in various ways. For example, topographic or contour information might be one layer, vegetation data may comprise another layer, with roads, power lines, gas, water and sewer lines on other layers, etc. For petroglyph records, different types of glyphs could be stored on different layers, variable glyph orientations could be layered or different glyph date periods could be stored separately. GIS systems are capable of storing hundreds of different layers.

Map features can be areas, lines or points. Features are usually assigned various "attributes" such as an ID, a name, area, centroid, perimeter, numeric, character, logical or date reference. Such attributes convey a variety of information about map features and can be displayed in many different ways. For example, areas might be shaded according to glyph density, according to topographic or geographic characteristics, or according to distance from the nearest housing development or roadway. Such maps are called "thematic maps".

The Petroglyph National Monument already owns the ATLAS GIS system. Locally, the National Park Service also uses the GRASS and the EPPL 7 systems. Any of these would provide an excellent opportunity for initial experimentation with storing glyph information and survey information on a GIS.

Although this type of software offers a variety of functions that can be helpful in rock art management and research, GIS systems are not appropriate for the storage of a glyph image database. GIS is not adept at the kinds of information retrievals and searches that are the primary interest of researchers and the main function of an image database. A GIS system is, however, likely to be an important part of an overall petroglyph survey and research project. It is unlikely, considering the present state of art that the image and the GIS databases can be integrated into one system with a single user interface. Initial data entry should be able to place information from the survey into both the glyph image database and a separate GIS system without significant extra effort. For example, the ATLAS GIS system is compatible with the dBASE database system. This means that if dBASE were used for the image database, the data (particularly the non-image data) would be compatible with ATLAS. Thus the map feature and attribute information could be entered easily into both systems. But it does not mean that a user, familiar with dBASE, could easily get at the information stored in the ATLAS system without learning the ATLAS command language.

b. Image Database Systems

A database is a collection of objects, composed of "records" which describe attributes or properties of the objects in question. The purpose of a database management system is to provide the secure storage of the data, to manage these data, allowing additions, updates and deletions, and to allow a user to easily retrieve any combination of selected data. Database software generally has a layered organization. On the hardware level, the system keeps track of the physical devices and addresses where particular data are stored. At the management level, the system provides utilities that create the database, handle functions that capture, store, retrieve, copy and delete these data. At the user level the system provides interfaces and languages that allow the user to interact easily with a set of information.

An image database is very similar to a traditional text database except that images require far greater storage capacity, which in turn complicates issues related to performance. Also, the types of update and editing operations likely to be performed on images are very different and diverse. Also, image databases almost always contain text or numerical data with image data frequently stored separately from text. Image databases differ depending on how tightly the images and text are coupled together, and as to the flexibility of the text and image access. Another special consideration for image databases is that of data compression. Extremely large gains in storage efficiency are possible for images, especially when using specially tailored routines that fit the image class. There are several data compression standards that can be used to transport data for use in other locations.

There are 5 major database structures. In the linear, sequential, or flat database, one record simply follows the next, like a stack of cards in a deck. This is the simplest structure, but is also the least flexible and has the slowest performance. The second is the hierarchical database which has a tree structure much like a family tree or taxonomy. There is a 1-to-many relationship between a parent object or family and its descendants or members in the tree. This type of structure leads to very high performance when the relationships are fixed and known ahead of time. It is cumbersome and low in flexibility when the relationships are unknown or are changing. A third structure is the network or threaded database in which there is a many-to-many relationship between records, allowing a record to be subordinate to multiple other records, in effect, the child of many parents. This is really just an extension of the hierarchical database and has essentially the same characteristics except it is more complex to maintain. The fourth is perhaps the most versatile database structure for image applications, this being the relational database. This database is organized as a series of tables which can be built ad-hoc as the system is created. This type of database has great flexibility but lower performance than the hierarchical type. The fifth type of database, object-oriented, allows data to be stored along with rules for data behavior and manipulation. The combination of data and behavior has great advantages in complex applications involving many different types of data and user interfaces.

A database system must support at least the following functions and behaviors. Acquisition, creation, and capture are the initial phases of building the database. Processing, manipulation, and revision are the continuing phases of database updating. Management, organization, and control are used to maintain, optimize and secure a database. Search and retrieval encompasses most user activities. Presentation, report generation, display, and hard copy result in the system's output. Interfacing and transfer functions support connection to other systems.

In the expected Monument recording project, the database is expected to perform several related functions. First, it will serve as an inventory of the resource and thus as a management tool. Second, it will serve as a source for educational materials. Last but not least, it will serve as a research tool. While the eventual results of the first two functions can be anticipated reasonably well, the research uses are more difficult to predict. Therefore, we expect the early uses and structure to be driven primarily by the first two goals.

In surveying the kinds of available commercial databases, there appear to be 3 major types. The first type is exemplified by PARADOX, DBASE, FoxPro, etc. These are PC-based database programs intended primarily as text databases, but also capable of somewhat limited image manipulation. These come in a variety of structures, and since they are PC based, they are widely used and therefore represent the most portable database format. They are also the type most users are likely to be familiar with. PC-based databases are relatively cheap. While there are similar products available on PCs and Macintoshes, at present there are not really any systems that offer complete interoperability on Macs and PCs.

The second database style are those intended for special purposes. Some are especially intended for image applications. These systems are available on a variety of platforms, including Macs, PCs and workstations (like Suns). They are generally more expensive and less widely used, thus less likely to be familiar to potential users. These systems are intended for image applications and frequently have image processing routines and data compression routines built in.

The third type of database system is one intended for research purposes and includes examples such as Ingres and PAD++. These systems are experimental and are likely to include the most interesting functionality and accessibility to the data. They are intended only for fairly expert users and are usually accessible only on workstations.

Factors to consider in database design:

Size and amount of data
Required access time
Complexity of access
Budget
Communications requirements
Indices of the database required
Information to be retrieved
Search criteria to be supported
Decomposition (What size pieces of images need to be retrieved) Manipulations of the text and of the images Reports to be generated
Training of users
Perceived benefits
Compression algorithms
Operating system & environment (PC, Macintosh, Workstation, etc.) Rate of change of project environment

2. Image Processing Routines

  1. Digital Contrast and Color Correction

One of the great benefits of digitization and computer manipulation of petroglyph images is this allows for contrast and color correction. Inclusion of a standard color target in every photograph permits inexpensive commercial software packages to correct the image for color balance. These packages can also do a limited amount of image sharpening correcting for poor focus or blurring caused by camera movement.

b. Stereo, Photogrammetry, Geometry and Correction

Photogrammetry is a method of making measurements of objects by photography. In particular, one can obtain full 3-D information about an object from sets of overlapping stereo pair photographs. This method can determine the 3-D topography of the terrain, the full 3-D relationships between petroglyphs in a panel complex, or a 3-D image of an individual glyph such as a face or mask that wraps around the corner of a rock. Perhaps the best use of stereo pair photography is in conjunction with computer graphics software that can display the 3-D information in a way that allows the user to interact directly with the image. Aerial stereo pair photographs can serve to construct detailed topographic maps. However, the full extraction of 3-D information is costly relative to the cost of conventional photography, and therefore there must be significant extra motivation to obtain the 3-D information. Photogrammetry is a technique that is widely used in the creation of topographic contour maps, but it has not found wide usage elsewhere.

3. Imaging standards and standards organizations.

Some standards will vary between scholars depending on their needs. However, to remain a part of the scholarly community, it is important to adopt standardized techniques.

ISO Technical Committee (TC) 171 - Micrographics and Optical Memories for Document and Imaging Recording Storage and Use.

Marilyn Courtot
Director, Standards and Technology
Assoc. for Information and Image Management Suite 1100
1100 Wayne Avenue
Silver Spring, MD 20910
(301) 587-8202FAX:(301) 587-2711

Image Technology (IT) 9 Committee on Physical Properties and Permanence of Imaging Media

Peter Adelstein
Image Permanence Institute
Frank E. Gannet Bldg.
P.O. Box 9887
Rochester Institute of Technology
Rochester, NY 14623-0887
(716) 475-2303FAX:(716) 475-7230

ISO Technical Committee (TC) 42 Photography

Eduard Scherrer
TAG/ISO 42 Administrator
NAPM
550 Mamaroneck Avenue
Harrison, NY 10528
(201) 825-0821

X3 - Information Processing Systems

Jean-Paul Emard
Director, Standards Secretariats, CBEMA 311 First Street NW
Suite 500
Washington DC 20001
(202) 626-5740

X3 Technical Committee X3B11 - Optical Digital Disks

Patrick Sandell
3701-A Berdrick
Rolling Meadows, IL 60008
(312) 705-1952

X3 Technical Committee X3L3 - Audio/Picture Coding

Charles Touchton, Chair X3L3
IBM Corporation
Suite 850/LKPT 8
Image Application Standards
3109 W. Martin Luther King Blvd.
Tampa, FL 33607
(813) 872-1075

Association for Information and Image Management (AIIM)

Marilyn Courtot
Director, Standards and Technology
Assoc. for Information and Image Management Suite 1100
1100 Wayne Avenue
Silver Spring, MD 20910
(301) 587-8202FAX:(301) 587-2711

National Association of Photographic Manufacturers, Inc. (NAPM)

Richard Hittner, NAPM
550 Mamaroneck Avenue
Harrison, NY 10528
(914) 698-7603

ISO/IEC JTC 1/SC 2/WG8 - Coded Representation of Picture, Audio and Multimedia Information

ISO/IEC JTC 1/SC 2/WG9 - Bi-Level Image Coding

ISO/IEC JTC 1/SC 2/WG10 - Photographic Image Coding

ISO/IEC JTC 1/SC 2/WG11 - Moving Picture Image Coding

ISO/IEC JTC 1/SC 2/WG12 - Multimedia and Hypermedia Information Coding

ISO/IEC JTC 1/SC 21 - Information Retrieval, Transfer and Management forOpen Systems Interconnection (OSI)

ISO/IEC JTC 1/SC 23 - Optical Digital Data Disks

National Institute of Standards and Technology (NIST)

James Burrows
Director, Computer Systems Laboratory
NIST
Technology Building, Room B154
Gaithersburg, MD 20899
(301) 975-2817

Working Group on Monitoring and Reporting Techniques for Error Rate and Error Distribution in Optical Disk Systems

Ferdinand Podio
Advanced Systems Division
NIST
Gaithersburg, MD 20899
(301) 975-2947

CALS/CE Information Center

Janet Geffner, Joint Ventures Coordinator NIST
U.S. Dept. of Commerce
Springfield, VA 22181
(703) 487-4648

V. HISTORY OF THE PILOT PROJECT

  1. The Search for a Pilot Study Location
  2. Criteria Our aim in selecting a pilot study area was to find a small, self-defining selection of petroglyphs. We wanted our sample to be clustered in an area naturally separated from other glyphs and made up a reasonably finite (small) number of images (about 50).
  3. Areas Considered Our initial selections were made up of about three or four clusters, each with its own advantages and disadvantages. These included a series of panels with hands, as well as a slightly larger and more varied selection deep within a canyon. We field inspected each location and weighed the options with reference to our objectives and goals.
  4. Final Selection Our final selection is close to a heavy concentration of glyphs to the north, but is separated from this cluster by a small space with few glyphs. Our pilot study location has a moderate number of glyphs that are distributed fairly evenly horizontally and vertically over the cliff escarpment. The glyphs in this area are reasonably diverse and interesting in their iconography and distribution. They comprise what appear to be a reasonably typical yet varied sample.
  5. First Version of Recording Forms

The first trial set of field recording forms was developed before doing much field work, before reviewing the photography from the Schmader study, and after examining only a handful of other recording forms. Our first set of forms lacked the means of pinpointing contextual relationships between images. This recording problem was not clearly addressed in our first efforts because we had not clearly defined it as a problem. Also, the recording hierarchy was not fully developed, that is to say, there was not a well organized relationship between forms. Another weakness was in the descriptive language we employed (or failed to employ) for glyph categorization and organization. We had not fully elaborated our ideas concerning the goals of the descriptive language or the potential for misrepresentation and bias in this process. See more on this below in section E and the section entitled 'Field Forms: Their Purpose and Function'.

C. Maps and Photographs

Our initial attempts to obtain maps of the pilot study site were not successful. The National Park Service was unable to supply maps at a large enough scale and the only other alternative, USGS 7.5 minute topographic maps are too large a scale to be useful. We found that the lack of proper maps severely hampered the planning of the field study and the recording and checking of glyph and panel locations. We highly recommend taking good aerial photos and making use of detailed maps before the commencement of any larger study. The budget for our small project was not sufficient to obtain these. During one of our early field sessions, we took ground-level photographs of the face of the escarpment and tried to use enlargements of these as a form of map. They were not especially helpful because of the low elevation angle of the escarpment (22 degrees) but they were better than nothing.

D. Photographic Recording Protocol

Many repeated trips to the pilot study area were made in an attempt to improve the recording efficiency of the field forms. We were interested in minimizing the amount of paper shuffling, and duplicate entries while increasing the relevancy of each form in relation to the complete package of field forms.

During this time, we were also particularly interested in developing a solid, scientific and systematic photographic protocol. We would like the photos to be as self-documenting as possible so that the images are auto-corrected for exposure, color and geometry. As a part of this process we also record film type, illumination, time of day and date. Reports of other field recorders were helpful in creating our photographic method, although we had to develop our own techniques for geometric correction. Procedures for color correction using known standard color targets is adequate, but the standard color target that is normally used has unknown color characteristics, particularly in terms of permanency. Nevertheless, we now feel our proposed protocol is adequate for this task.

If we use a digital camera, a period of familiarization and testing will be needed to ensure that our proposed methods fulfill recording needs.

E. Recording Form Revision

The maturation of our field methods and the development of the field form packet took place over a period of several months and unfolded through a pattern of field tests, discussions, and subsequent changes. While we were field testing our protocols, we were also discussing field methods and objectives through our interviewing process described elsewhere in this report. We paid repeated visits to Jay and Helen Crotty because of their ongoing activities with the New Mexico Archaeological Societies summer rock art field school. Their experiences with the field school over the last six or seven years was extremely valuable to our own field recording progress. Our own field recording methods evolved into an hierarchical series of steps that begins with an overall site form and proceeds through a nested set of forms that records progressively smaller units of the site until reaching the final form that inventories individual glyphs. We spent much time agonizing over our descriptive vocabulary for glyphs. In order to get some idea of what we were dealing with we examined about 1000 of the glyph photos at the park's visitor center. While looking through this collection, we discussed descriptive options and tallied glyph frequencies. In this way, we created a listing of categories and types, weighted toward evenness of occurrence and descriptive clarity. As we compiled the glyph list, our attention turned naturally to the intent and function of this typology. This subject has also been the object of considerable agonizing and hand-wringing among rock art scholars. This is because the objectives, intent, and meanings for most petroglyphs and pictographs remain elusive, enigmatic and indecipherable. That leaves those attempting to record rock art with an impossible task, one of identifying, labeling and organizing glyphic images without a key, that is, without having more than a clue how to accomplish this task. With this in mind, one can only take the first rudimentary steps of organization and sorting. Images can be separated and lumped by observable characteristics as a first analytical step. Scholar's real concerns have been with labeling apparently representational images without knowing much about their purpose or context. Facing these issues, those recording rock art have only one option, to label both representational and non-representational images as best they can, using a clear and concise descriptive language, and making it perfectly evident that these labels are nothing more than organizing tools. Our present edition of glyph descriptors is simply a working catalogue, due for revisions in the future.

F. GPS Study

Our initial investigations of GPS (Global Positioning System) as a possible technique for determining glyph locations were disappointing. Inexpensive units such as the Trimble Pathfinder Basic Plus are able to locate a point within 2-5 meters. Unfortunately, we were interested in an accuracy of 1 meter or less, but 3 factors led us to examine the less expensive units. First, the Park Service already owned some of the inexpensive units and made them available to us. Second, we needed some field experience with GPS units of any kind to appreciate the simplicity or difficulty of their use. Third, more accurate GPS units at that time were very much more expensive ($50,000.).

Initial experiments with the inexpensive Park Service units led to several difficulties. First, the Park Service software was out of date and did not work with current satellite almanac data for planning and differential correction. Second, the Park Service was not always able to supply us with reliable base station data. Third, the GPS units would not work properly in the field with either the internal antenna or external antenna at ground level. They would only work when the external antenna was hoisted atop an 8 foot high pole. Apparently this was caused by "multipath" problems from the local topography. These are multiple signals, some of which bounce off the terrain's basalt boulders, thus confusing the GPS data.

All of these difficulties were eventually overcome, but they do illustrate the problem of new and untested technologies that frequently cause added problems during the start-up phase. When the measurements were eventually made, they showed that points could be measured with an expected accuracy of 2-5 meters. This was established by locating a set of 8 points on the ground during three different days with three different satellite configurations.

Subsequent discussions with GPS professionals have led us to believe that newer, more precise units are now becoming available at a moderate price ($10,000.) that are capable of sub-meter accuracy. Such units would not eliminate the same multipath problems, but with the external antenna used on a pole to raise it at least 8 feet high, we can expect to achieve sub-meter accuracy.

G. Computer Studies

The only computer system the Park Service made available to us was in a fairly public area of the Visitor Center, had no security capability and was accessible by a wide user population. Because of this, we decided to do most of our development on our own computers, a MAC Powerbook, a 80486 PC and a UNIX system. These computers had image capability, enough storage and provided for experience on a wide variety of computing platforms.

The computer studies included the installation and operation of the Trimble GPS planning and differential correction software, and the uses of Adobe Photoshop image processing software, the Paradox Database program, Hewlett-Packard Deskscan II scanner software, UNIX X-Windows image processing software and the development and use of several home-grown software routines for image processing, geometry correction and color correction

With these computers and software programs we have demonstrated the feasibility of digitizing images, transferring them from computer to computer in a number of standard image formats (both uncompressed and data compressed), correcting the images, and formatting them for use in the database. We can move the images in and out of standard packages like Adobe Photoshop, prepare the images for publication and get hard copies of the images.

Finally, we were able to add the images to a Paradox database that is structured hierarchically, just like our recording forms. The database was able to hold site photos, view photos, panel complex photos, sketches and small maps as well as the glyph photos. Photographs are stored as image fields in the relational database and are retrievable along with all of the non-image data relevant to the particular photo. Searches of the database can be conducted for all glyphs of a particular type, of a particular orientation, in any location or according to any combination of criteria. The database for the pilot study is too small to be really useful or impressive yet, but it does demonstrate the feasibility of a research tool that is a quantum leap in usefulness over the present "shoebox" method of image storage.

H. GIS Systems

The National Park Service now owns the Atlas GIS system and maintains it on a computer at the visitor center. We tried to apply it but there was no map data available to form a basis for its use. We were led to believe that several people were using this system for their studies but were not able to find their information. We also obtained the GRASS GIS system, which is a public domain software package maintained by the Corps of Engineers and used heavily by the Park Service. We are now in the process of installing and testing this system. When it is running, we hope to get some map data in a compatible format from the Park Service.

I. Field Forms: Their Purpose and Function

One of the important facets of this project has been to develop a working set of field recording forms. The purpose of these forms is five-fold: to record all data relevant to management and preservation requirements, to make the field recording process as timely as possible, to organize the data so that it can be easily elaborated and manipulated, to offer an open-ended database structure that will aid rather than impede research, and to make a first stab at developing a uniform, inter-site recording format and process.

The field forms were initially put together through a process of relating personal field experience with data gathered from other rock art field recording forms. Our original forms were then put through a number of field tests and thus evolved through a series of iterations. The next step will be to forward our present generation of forms to a number of scholars and resource managers for comment. Although we feel we have come a long way in the design of our field form package, we realize further changes are inevitable once a concerted effort to record Petroglyph Monument's resources begins in earnest.

The forms are hierarchically organized, from general to specific, beginning with the 'Rock Art Site Form' which is an overarching description of the entire rock art site. The other four forms are increasingly specific in their content and context, in the following order: 'Rock Art Unit Form', 'Petroglyph Panel Complex Form', 'Petroglyph Panel Form', and 'Glyph Form'.

The field recording of petroglyphs does not conclude the recording process. In the field, rock art images are simply sorted into categories of descriptive convention. This procedure may in fact lump or divide elements or motifs that may later be reorganized, separated, or combined. At this stage of our knowledge, the recording process can be nothing more than a first and admittedly crude attempt at classification and organization. On the other hand, the contextual documentation of the data must be done precisely in the field. There are no second chances with this class of information.

As a matter of course, data will be taken from the field forms, coded, and transformed into an automated database. The automation of this database will eventually provide the means for the first systematic analysis of a significantly large body of rock art.

The 'Rock Art Site Form', 'Rock Art Unit Form', Petroglyph Panel Complex Form', and 'Petroglyph Panel Form' are meant, with minor alterations, to serve as uniform inter-site data records. With the minor alterations described below, the 'Rock Art Site Form', and 'Rock Art Unit Form' should function for both petroglyphs and pictographs. The 'Petroglyph Panel Complex From', and the 'Petroglyph Panel Form' are designed specifically for petroglyphs as their names imply. Functionally similar forms can be created for pictographs that will be structurally compatible with the petroglyph forms. Finally, the 'Glyph Form' is designed to be site or at least regionally specific. The function of this form is to organize the data into workable units of relatively equal size. Moving from site to site, this form can be altered, but will remain structurally and functionally equivalent.

The 'Rock Art Site Form' serves as the counterpart to an archaeological site form. On the positive side this gives the recording of a rock art site a certain compatibility and uniformity with archaeological protocols. Unfortunately, archaeologists have come up with countless ways and means to define a site, leaving this issue far from resolved. Leaving this problem aside for now, Petroglyph Monument may be considered a single site or divided by various means, whatever best serves the interests of those recording the monument.

There are four major categories of information on the 'Rock Art Site Form', 'Location', 'Description', 'Environment', and 'Culture'. 'Location' includes a 'site number' as well as overall site location and dimensions. There are several categories for location: 'GPS Coordinates', 'UTM Coordinates', 'USGS Map', as well as 'Township', 'Range', and 'Section'. Archaeological sites are normally located by UTM's, USGS map and sectional information. GPS and UTM coordinates are records of overall site location and dimension. The final entry in the 'Location' section, 'Site Dimensions' will include these dimensions in meters.

The next category, 'Description', #2, is simply a general description of rock art type, whether it includes petroglyphs, pictographs, or both.

Category 3, the 'Environment', includes the type of surface used for rock art, as well as nearby vegetation and hydrology.

The next category, number 4 - 'Culture', is more or less specific to the Rio Grande Valley or other places of Pueblo or Historic Hispanic Occupation. This category of information is easily altered as is any category on this form since there is only one per site. Following the 'Culture' entries is information about the recorder and photographs. For the site form, this should include only general site photographs, either aerial or perhaps wide-angle.

Following the 'site' designation is the 'Rock Art Unit Form' in the descending hierarchy of field forms. In the hierarchy, the 'Site' is made up of any number of 'Units'. Such units may be either laid out in a grid or be organized around petroglyph concentrations. In Petroglyph Monument, there are clear rock art concentrations which may be considered as 'units' or further subdivided into smaller, and perhaps more manageable 'unit' sizes. Only one 'Unit Form' needs to be completed per unit. The 'Unit' form accomplishes two objectives: to organize and subdivide the 'Site' into smaller working segments, and to locate individual rock art images and image clusters, in this case, on a gridded map included on the 'Rock Art Unit Form'. Besides the map grid, the 'Unit Form' is divided into two sets of information, 'Location' and 'Description'. The 'Location' entries include 'Unit Number', 'Site Number' which also appears on the 'Rock Art Site Form', as well as 'GPS Coordinates' (that define the unit boundaries), 'USGS map', 'Unit Dimensions', 'Unit Photo #', and unit photo 'Direction'. The "Unit Photo #' should be a general landscape photograph of the unit. The second category, #2, 'Description', is a general classification of the rock art and the techniques used to produce it. Included are techniques for petroglyphs only since pictographs are simply painted. The grid map includes an entry for 'Scale' below the lower right hand corner of the grid.

The next form in the hierarchy is the 'Petroglyph Panel Complex Form', the first of the petroglyph-specific forms. A 'Unit' is made up of a number of 'Panel Complexes' noted on the 'Unit' map by letter, number, or some other designation. Included on this form are 'Panel Complex #', 'Unit #' (for the 'Unit' within which the 'Complex' appears), 'Panel #'s' ( for Panels within the 'complex'), and 'Panel Position'. 'Photo #(s)' is an entry for a photograph of the 'Complex'. The set of entries under 'Type of Complex' describe means by which panels may possibly be associated. These options include 'Thematic Unity' that refers to similar images over a number of panels such as a series of hands or masks, 'Joined' that applies to petroglyphs joined by lines or other images, 'Multi-Panel Alcove' indicates a set of panels oriented around an open space, perhaps intended as a single gallery, and 'Multi-Panel Boulder' is a series of panels on various faces of a single boulder. A 'Site Map' space is included on this form in order that a small sketch of the 'Complex' can be included. This may either take the form of a frontal elevation, an oblique overhead, or a straight overhead view, whichever transmits the more information.

Next is the 'Petroglyph Panel Form', divided into four primary categories of information, 'Location', 'Petroglyph Description', 'Cultural Context', and 'Condition'. 'Location' includes three sets of numbers, 'Unit #', 'Panel Complex #', and 'Panel #'. Also under 'Location' are 'Panel Dimensions', 'Compass direction of Panel', 'Base of Image from Ground', 'Inclination', and 'Number of Glyphs'. 'Compass direction' refers to the direction in which the panel faces, given in degrees. 'Inclination' is a measure of the panel's verticality, gauged from the horizontal plane and again given in degrees. The next set of categories is #2, 'Petroglyph Description'. The first of these entries is 'Superposition' with a yes-no option. 'Glyph Complex' also has a yes-no option and is followed by a series of choices if the answer is yes: 'Joined' refers to images joined by lines or other means, 'Wrap-around' applies to images that extend from one panel face to another such as masks, 'Scene' refers to isolated images which appear to be interacting or are clearly meant to be associated, and 'Thematic unity' implies that a series of images seem to be of a similar type such as a grouping of quadrupeds with antlers or masks, etc. Category set #3 is 'Cultural Context', adapted in this case to the Rio Grande Valley and Petroglyph Park. Number 4, 'Condition', is repeated on the 'Glyph Form' in category #11, 'Recent Graffiti and Vandalism'. The 'Threatened By' entry refers to evidence of recent and increasing vandalism, adjacent urbanism, recent erosion, etc.

The final and most specific field form is the 'Glyph Form' which includes entries for two types of data, a 'Glyph # - Code#' and a glyph descriptive 'Element Tally'. The 'Glyph # - Code#' is a number/letter code for each entry in the 'Element tally' listing. The 'Element tally' is an individual description for each glyph that is divided into eleven sub-categories. The first four of the subcategories are non-representational, geometric classes. Numbers 5 through 8 and 10 are presented as representational descriptions but as data classifications are really no different than the non-representational entries. In both cases our classifications are intended to imply nothing more than images that look on the one hand like arcs and lines (non-representational), or birds and human hands (representational) on the other. Non-representational images simply do not look like anything we presently recognize using our visual and cultural conventions. Whether or not non-representational images depict a separate class of information remains to be seen.

The first data set are 'Single or Parallel Lines'. These are more or less selfevident except perhaps for 'Spiral or scroll'. A 'scroll' usually refers to an interlocking, double spiral, whether curvilinear or angular.

Entry set # 2 is 'Branched Or Intersecting Lines'. The second entry is 'Rake' which is a single line, touched or intersected by any number of short, lateral lines. A 'Ladder' is similar, but with two usually parallel lines intersected or touched by shorter, lateral lines. 'Dot Patterns' of classification set # 3 are selfevident. Number 4, 'Closed Geometric Forms' include closed rectilinear and curvilinear elements, understandable in their description except perhaps for 'Double triangle', 'Joined triangle 'saw'', 'Concentric circle', and 'Nucleated circle'. A 'Double triangle' is usually joined at opposing points, much like two arrowheads touching at their tips. 'Joined triangle 'saw'' refers to a series of triangles attached to a single line that give the overall appearance of a saw. A 'Concentric circle' is a series of nested circles around a common center, whereas a 'Nucleated circle' surrounds a central nucleus.

The next series of entries are of apparently representational images. The first of these entry sets are, #5, 'Human/ Anthropomorphic Figures'. The first three of these, 'Frontal stick', Frontal outline', 'Frontal infilled' refer to different methods of depicting apparently human figures. The next three are the same, but in profile. 'Partial or torso' figures are those that appear to be human representations, but incomplete, either lacking arms, legs, or lower body. A 'Therianthrope' is a figure with both human and animal attributes. The next class of descriptors, 'Animal Figures', #6, begin with three 'Quadruped' (four-legged) representations, 'stick', 'outline', and 'infilled'. The meaning of other entries in this category should be apparent. All entries in category set #7, 'Prints and Tracks' should also be self-evident. Category #8, 'Cultural Symbols and Plant Forms' is a catch-all for remaining representational imagery. A 'Blanket design' is a primary catch-all, referring to complex patterns that are similar to Puebloan weaving motifs. A 'Shield' is a circle with enclosed and/or appended elements, often quite elaborate. On occasion, 'Shields' appear with a frontal human figure standing to the side, apparently holding the shield. A 'Club or ax' is an apparently hafted object, commonly on a long handle. There are a number of 'Arrow' petroglyphs that appear to be clear representations. The same cannot be said for 'Corn plant' which is something of a catch-all for images that seem to be stalked plants, some of which are more corn-like than others. 'Elaborate misc.' encompasses everything that does not fit elsewhere in this set of entries. It can include what appear to be ceramic designs and motifs as well as other singular and elaborate constructions that occasionally occur. 'Star figure', 'Star head', and 'Star' all appear with some consistency, and may turn out to be different manifestations of a single being or concept.

Category #9, 'Indeterminate', encompasses several kinds of image. 'Indecipherable/light' applies to anything that is either too worn to distinguish or is simply indecipherable and cannot otherwise be classified. 'Scattered dots' are marks that seem to be randomly placed with respect to each other or other images. A 'Smoothed surface' is one that has been ground smooth, either on horizontal or more vertical surfaces. These are not necessarily petroglyphs, but may have served as grinding surfaces.

'Historic Images and Inscriptions', Category #10, includes everything historic other than recent graffiti. A 'Christian cross' is often found engraved over, or on top of, prehistoric imagery. A 'Church' is a cross mounted on a rectangle or single stepped pyramid. An 'Anthropomorph' in this category set is one with some identifiable historic accouterment, either a rifle, brimmed hat, mounted on a horse, etc. 'Names/dates' here are those older than fifty years. 'Stock brand' is either a sheep or cattle brand, many of which have been identified and associated with a ranch or rancher. 'Recent Graffiti and Vandalism, #11, is the final group of entries. It includes any inscriptions more recent than fifty years as well as other forms of vandalism that include 'Defacing', 'Bullet holes', and 'Rock removal'.

VI. DEMONSTRATIONS

This section reviews the status of various demonstration tasks that we entered upon as part of this project. Our objective was to establish the feasibility of a number of experimental techniques and technologies for the recording and storing of petroglyph images and data. We believe that most of the really crucial or risky methods and technologies have been demonstrated with enough thoroughness to prove their practicality. However not all possible technologies or methodologies have been demonstrated. We review several possible demonstrations below that have not been attempted but that may prove useful before a full scale project is undertaken.

  1. Photography

The glyphs in the pilot study area were photographed with a conventional 35mm camera and with color film using natural daylight illumination. The resulting prints were of a quality sufficient for digitization and archival storage. The quality was significantly superior to that of the Black and White photography obtained from the Schmader study [8] and the color images of the Eastvold survey. We developed methods for color correction, for recording of object scale, and for the angle of film plane to object plane. The use of natural illumination made it necessary to return to rephotograph some petroglyphs because of poor lighting. This necessity would be eliminated by the use of a sunshade and flash photography. Flash photography was adequately tested in areas that were naturally shaded.

B. Digitization of Photographs

All photographs of glyphs in the pilot study were digitized using a desktop scanner and stored as "*.tiff" files in the computer file system. Our scanner is a Hewlett-Packard Scan-Jet IIc which is attached to a PC in the Computer Science Department at UNM. It is available to all students and researchers. The PC is connected to our departmental network and the images can be transferred easily to our UNIX workstations. The images were digitized at the highest resolution our scanner could use which was 200 dots-per-inch. It should be noted that higher resolution scanners are now available at a reasonable price. This digitization produced image files that were usually about 1/2 million pixels in size (about 600x1000). The images could be digitized at 24 bits/pixel (true color, 3 bytes/pixel) or 8 bits/pixel (1 byte/pixel). For this work, 8 bits/pixel was used and seemed to give satisfactory results. As a generally rule, each image file initially takes about a half megabyte to store. In preparation for insertion into the image database, a UNIX and X-Windows based image processing package called "xv" was used to modify the contrast and color balance, if necessary. This package was also used to reduce the resolution of the image down to about 100x100 so the experimentation with the database would be more efficient.

A very brief experiment was carried out with the Kodak Digital Camera. Pictures were taken in the state park area of the Petroglyph National Monument and those pictures were later loaded onto disk and printed out on a hard copy. The results seemed satisfactory but more experimentation would be needed before such a camera could be recommended.

C. Storage of Images and Non-Image Data in a Database

The various images and data from the pilot study have been entered into an object oriented relational database (the Paradox software package) on a PC. The database is hierarchically organized with site entries, unit entries, panel complex entries, panel entries, and glyph entries. The data in the computerized database parallels the data format shown on our recording forms. Paradox was selected as the underlying database package because it is an object-oriented, relational database which seems to fit the natural organization of our database. Also, Paradox allows construction of DBASE oriented indexing information which is compatible with the Monument's Atlas GIS package. Finally, Paradox is appropriately inexpensive for our initial feasibility study. It should be pointed out however, that eventually a more sophisticated and specifically designed database will be necessary to manipulate the full data package.

The images in this database are stored in their "*.tiff" format alongside with and as accessible as non-image data. The data entry process is very efficient but requires a moderately sophisticated user. Data entry forms and interfaces can be developed so that an untrained user can do data entry, but this was not done as a part of this demonstration.

D. Retrieval of Images and Non-Image Data

Once the database was constructed, the images and the non-image data could be retrieved in a number of ways, using different search keys such as glyph type, location, orientation and size. Retrieval of the image occurs right along with the retrieval of the non-image data similar to any regular database.

Once again, the retrieval process is very efficient but requires a moderately sophisticated user. Retrieval forms and questionnaire interfaces can be constructed so that an untrained user can do retrieval entry.

E. Modifying Non-Image Data

When particular records in the database (such as a single glyph entry) are retrieved, the non-image data is immediately available for editing. Fields in the record can be modified quite easily. Addition and deletion of fields is also fairly easy to accomplish. Modification of the image data is more complex and is discussed in the next section. Modification of the overall structure of the database can be accomplished, but frequently involves a significant new amount of data entry. Thus it is best to have a good idea of the best overall structure of the database before it gets very large. No special interface for data modification was created, but it is possible to develop and interface so that an untrained user can make simple modifications.

F. Editing of Images

It is possible to have the database program invoke an image editor when a particular glyph record is retrieved and the image field is entered. A special image editor is needed because image editing is a more complex process than editing and modifying regular data. For example, the database could invoke a program like Adobe Photoshop. We have demonstrated the ability of Photoshop to read and write image formats such as *.BMP, *.TIFF, *.GIF, *.EPS, JPEG, PhotoCD and others. Photoshop allows one to crop, cut and paste, paint and label the image, rotate and scale, magnify and reduce, color correct, adjust brightness and contrast, sharpen and smooth, dodge and burn, construct composite images and generally prepare images for publication. There are many good image processing packages like Adobe Photoshop but it is one that is widely available.

G. GPS Data

A test of basic GPS capabilities was carried out. It was expected that accuracy of about 2-5 meters was possible a level of precision too low for glyph location. However, there are more accurate GPS systems, but before recommending such systems, we thought it useful to use the readily accessible basic systems to see if the expected accuracy could be achieved.

Our GPS system was a Trimble, Pathfinder Basic Plus unit. It comes with the Trimplan mission planning software and Pathfinder data analysis software. We used the Trimplan software to plan periods of good satellite coverage. At first, with the built in antenna and with the external antenna hand-held, we could not get accurate readings. Then, with the external antenna mounted on a 8-foot tall pole, we were able to get good, accurate readings. We concluded that the local topography near the escarpment was causing multipath errors for the GPS receiver. This would be a problem even for more expensive GPS units. We used the Pathfinder software package to analyze the recorded points and plot the results. Trips to the location on three different days, using three different satellite configurations showed that accuracy of about 2-5 meters could be achieved.

H. Location

In addition to trying the GPS units for locating the glyphs, we also tried the old fashioned methods of climbing over the rocks with a tape measure to record distances, using a compass to sight angles for the glyphs. This method was able to produce 1 meter accuracy, but was prone to multiple errors, was time consuming, and produced an unfavorable impact on the fragile soil and plant communities surrounding the glyphs.

VII. SUGGESTED DEMONSTRATIONS

The following is a set of tasks we would hope to carry out prior to the full-scale recording of the entire monument.

  1. Digital Camera

There seem to be many potential advantages of using this equipment and although the initial cost seems high, there are long-term cost savings. A digital camera should be field-tested for at least a month (perhaps with an option to buy) as a prelude to field recording. We need to know if it is rugged and dependable for field use, if it takes consistently good images, and if it can be used to digitize old prints and old slides. We also need to test the batteries, the interface, and the supplied software.

B. Dating

The Monument should contract with outside experts for this activity, namely Ronald Dorn from Arizona State University. Perhaps we can also obtain some volunteer assistance from Sandia National Labs.

C. GIS Database

The Petroglyph National Monument has the Atlas GIS system. A project should be undertaken to set up a GIS database for the entire monument, especially for the area and the data obtained from this pilot study. In particular, an interface should be set up to build the GIS database from Paradox data images and coded information.

D. Ethnography

Ethnographic data must be a very important part of full blown recording project, but as yet we have not explored the most elegant way to integrate this information into the rest of the data. There are several possibilities in terms of data integration. The ethnographic data can be kept completely separate. This data can also be stored separately but be indexed along with the rest of the data with references to glyph, panel, panel complex, and unit records. Finally, the ethnography can be completely integrated with the image and text data. The final option would require more multimedia capability in the system, more storage and more complexity in development. Thus, the last option of full integration would be the most expensive but will produce by far the most useful research mechanism. At this stage it is difficult to estimate the cost of such a system although a small project to do this would be very useful.

Ethnographic data will likely be stratified as to its confidentiality. Certain, specified records may be accessible only to Pueblo people. Other data may be restricted to professional scholars. Confidentiality and subsequent restrictions will be dictated by Pueblo religious leaders, some of whom will probably be involved with the recording of the Monument's petroglyphs. Images of a sensitive nature will be withheld from publication and avoided by Park visitors if possible.

E. Staffing

We have carried out all the activities in this pilot study by having the principal investigators do all the work. Needless to say, this is impractical for the full project. We need to test the kind of staffing that might be needed for complete recording. This includes each of the field recording teams (4-5 people each?) and the data processing and database entry team (2 people?).

F. Bigger Database & Jukebox Hardware

The present database contains only about 50 images. It will be useful to expand this number by a factor of about 10 to observe the effect on overall efficiency. A database of about 500-1000 images would allow us to test an external optical disk or jukebox storage device similar to what might be needed for the whole database.

G. Database Interfaces

During the course of this project, we have demonstrated the feasibility of various parts of the data processing, but have not built any easy access interfaces. Userfriendly interfaces are needed to move data between the database and the GIS system (Atlas or GRASS). Other interfaces are needed to get data from the digital camera and/or the scanner into the database. Another interface will be required to download data from the field laptop into the database. Further interfaces are needed to produce hard copy reports on the progress of the database and GIS entries.

H. Cost Factors

Better estimates of the cost factors for the entire project are needed. The computer and field equipment estimates are relatively well known for present prices, but by their nature, these prices are changing rapidly and must be constantly updated. Cost factors for personnel, field recording, and data entry have not been estimated.

VII. COST ESTIMATES

RECORDING HARDWARE

Laptops: These units can be used in the field to record the textual data, to field check the photography, and to check the locational data. Using laptops in the field avoids the costly, time consuming and error-prone procedure of transcribing the data from field notes on paper into the computer. Another benefit is the ability to field check the data and to avoid the costly necessity to return to a site if the data is bad. A typical laptop now costs $1,500.-$2,000.

Electronic Distance Measuring Devices: Use of this kind of device can be very efficient in obtaining fast and reliable location data for the petroglyph panels. Measurements can be entered into the laptop computer in the field and quickly checked for accuracy and validity. Such a device costs about $1,500.

Surveying Total Station Equipment: Such a station can be used to lay out the base lines along the bottom and top of the escarpment. It might also be the most accurate and cost efficient method of locating the individual glyphs and panels. Such a station and its ancillary equipment will cost $7,000.- $9,000. An added data collector to program the measurements and automate the down-loading of location data costs an added $2,500-$3,000.

GPS Station: A GPS unit capable of sub-meter accuracy (after differential correction assuming a nearby accurate base station) would cost $10,000.

Digital Camera: These cameras should be used to photograph glyphs, panels, complexes and units. The alternative and historically more typical way of doing this is to use 35mm camera and film. The film must be purchased, exposed, processed, scanned into the computer and then color corrected for the processing. Only then can the recorder determine if the photo image was successful The cost is about $1.50/shot. With the digital camera, equivalent quality images can be obtained for approximately the same cost while the scanning step is eliminated. Further, the results can be field checked. At present, the best camera of this type is the 2 Kodak DCS200C. The Kodak camera costs $10,000.

COMPUTER HARDWARE

Central Database Computer: Since the emphasis of the anticipated project will initially be on the recording process, only a fairly simple central computer is necessary. This requires inexpensive PC computers with large memory capacity. One major problem will be the necessity of purchasing an extremely large storage capacity for the 10,000-20,000 images. Each image will require at least 1 megabyte of storage so that the total storage required will be from 10 Gigabytes up to 50 Gigabytes. This is best handled by optical disk storage technology for the storage of images off-line. It will be best to use low resolution and compressed versions of the images on-line. Such a computer station would cost about $5,000.-$7,000.

Color Hard copy Printer: $5,000-$8,000.

SOFTWARE

All of the software required for the recording, calibration, correction and storage of the database is available in standard commercial software packages or in widely-used and well supported public domain packages available on the Internet.

The image acquisition and correction software might be Adobe Photoshop which is the most popular package for this activity and is included bundled with many commercial scanners. Photoshop costs about $500.

The image database should initially be constructed in a commercial database management system such as Borland Paradox, Dbase IV, or Microsoft FoxPro. The main advantages of these systems are that they are inexpensive, widely available and if we eventually decide to use a more sophisticated database or to transfer the data by computer network to other sites, these systems allow easy portability of the data. Paradox costs about $150.

The GPS planning, transfer, correction and averaging software will be Trimble Pfinder software purchased with the GPS equipment. The geographic data obtained from the GPS data will be entered, stored and displayed using GRASS, a widely-used public domain GIS system.

SPACE

About 200 sq-ft would be required for a work station. Space also may be needed for field equipment storage.

STAFF

A recording team of about 4-5 seems most efficient. This team could work at least 5 hours per day in the field. The rest of the day each team could do maintenance, field preparations and data entry.

RECORDING TIMETABLE

It seems to take about 15-20 minutes/panel for our pilot study. We do not yet know how much more efficient we can get with a larger team and after more practice with successful procedures. If we assume there are a total of 5000 panels, this means the total project would take 100,000 minutes or 1667 hours or 333 5-hour team-days to accomplish.

IX. RECOMMENDATIONS & CONCLUSIONS

RECORDING OF EACH PETROGLYPH

We recommend either of two options. One, that another, larger-scale pilot study be undertaken with a goal of recording about 500-1000 glyphs. A second option is to undertake the full recording program with at least a six-month start-up to accomplish what would otherwise be done in another pilot study. The largerscale pilot study would refine some of the mapping and locational techniques, test the use of the digital camera and laptop in the field and test the use of a recording team of 4 people. This proposed project should then record in a variety of areas including a very densely packed glyph complex, a very sparse area, and several specialized areas with unusual glyphs, complexes or other unusual topographic or archeological characteristics. Consultants from other research groups have been invited to review the recording procedures and this process is anticipated to continue throughout the recording period.

Before any major recording project commences, aerial photography with a resolution of at least 1 meter should be obtained. If possible, this will then be used to produce contour maps with 2-5 meter contours.

Before any project begins, the recording forms will be implemented as a recording questionnaire form in the laptop computer.

The first step in any recording should be to lay out a baseline of known fixed positions below the escarpment and mark this with stakes. Units should be tagged every 50 meters.

Each petroglyph panel should be recorded by a team of about 4 persons, including a Photographer, a Location or measurement specialist, a Text Data Recorder, and a Team Leader who will help with all other aspects of the recording, including bearing and inclination, and panel and rock sizes. One of the 4 will draft the plan and elevation views for panel complexes. If a total survey station is used to record positions, another person will be needed to handle this task along the baseline.

Photographs of each panel and perhaps individual petroglyphs, and panel complexes will include an "up" arrow, a title board including the photograph index number, color correction and geometric scales. Recorded photographic data will include film type, exposure parameters, lens, filter and lighting parameters, and optical geometry parameters. Date and time of day will also be recorded. Identical photos will also be taken without the scales and title board.

Text data will be recorded directly into a laptop computer. Textual data to be recorded includes a description of the rock on which the panel occurs, including size, shape and panel surface parameters and distinguishing features. Also recorded will be the panel size, shape, flatness and orientation (bearing and inclination). If deemed necessary or helpful, a drawing of the panel, petroglyph or local site will be made.

Location data recorded will include X, Y and Z UTM coordinates.

Experiments conducted during this study, indicate that with a team of this size, a typical panel can be recorded in about 20 minutes. Experiments also indicate that substantial benefits in terms of recording accuracy and time savings occur if the photographs are recorded directly by a digital camera and checked for quality in the field. Speed and accuracy are also enhanced by directly entering textual data into a laptop computer onsite. GPS, survey or distance measurement data should always be recorded in digital form and directly downloaded to a computer.

In addition to recording the individual petroglyphs and petroglyph panels, a number of other activities must be carried out to support the recording process.

There will be a data entry team at a central lab whose function will be to load each days data from the field computers into the central database computer and ensure it is verified and is backed up to prevent loss. This team will also have to do the processing of the location data.

REFERENCES:

[1] Wainwright, Ian N. M., Rock Painting and Petroglyph Recording Projects in Canada, APT Bulletin, The Journal of the Association for Preservation Technology, April 1989.

[2] Texas Parks and Wildlife Department, Rock Art Recording Manual, 1992

[3] Bahn, P. G. & Vertut, J, Images of the Ice Age, Facts on File, NY, 1988.

[4] Ogleby, Clifford L., Digital Technology in the Documentation of Rock Art, 2nd AURA Congress, Cairns, Australia, September, 1992.

[5] D'Alleyrand, Marc R., Handbook of Image Storage and Retrieval Systems, Van Nostrand Reinhold, 1992.

[6] Gonzalez, Rafael C. and Wintz, Paul, Digital Image Processing, Addison Wesley, 1987.

[7] Ogleby, Cliff and Rivett, Leo J., Handbook of Heritage Photogrammetry, Australian Heritage Commision, 1985.

[8] Schmader, Mathew F. and Hays, John D., Las Imagines, The Archeology of Albuquerque's West Mesa Escarpment, Open Space Division, Parks and Recreation Division, City of Albuquerque, 1987.

[9] Moore, Terry D., Computer Enhancement of Digitized Images Using an IBM or Compatible, A Practical Guide, Terry Moore, 10361 Cliota, Whittier CA, 1992.

[10] Loendorf, Lawrence, Olsen, Linda and Conner, Stuart, A Recording Manual for Rock Art, Department of the Army Contract #CX 1200-7-B061, 1993.