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Artifact Photogrammetry

 

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In 1996, with support from a grant by the National Center for Preservation Technologies and Training, CAST conducted  research to develop an easy and inexpensive method to generate 35mm stereo photographs of archaeological artifacts from which three-dimensional measurements could be extracted using a digital (or softcopy) photogrammetry workstation.  A complete copy of the final report in PDF format is available here. 

As part of this effort, photographic and photogrammetric issues were addressed so as to identify the conditions necessary to create photographs suitable for a softcopy photogrammetry system. In particular, various lighting systems and film types were tested, as well as mechanisms to control camera movements and to create a "virtual" three-dimensional reference (coordinate) system around the objects photographed.

Results obtained with this method proved comparable in accuracy and consistency to those taken manually by archaeologists when small to medium-sized objects are considered (e.g. arrowheads and beads). For larger objects, such as pots, the error introduced in depth measurements, by non-calibrated standard 35mm cameras proved larger. This can, however, be remedied by taking photographs from several angles.

Such a method could have a significant impact in data collection efforts where one is able to view an object in 3-D even when the latter is no longer available. Federal and state organizations responsible under NAGPRA for the return artifacts to Native American groups could definitively benefit from using this method.

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Abstract

For as long as institutions and individuals have been obtaining, collecting and storing prehistoric and historic materials they have struggled to find and implement a good, usable, reliable and transferable method for increasing the usefulness of their collections. In the past the public and researchers would need to travel to a museum or other collections repositories to study materials in any detail, particularly to obtain measurements of the objects. However, travel was costly and the measurement process often exposed the object to damage through handling. In other cases objects that have been placed in public museums or repositories may no longer be accessible for such studies since they may be removed as a result of repatriation.

Modern technical developments in computerized, softcopy photogrammetry now can address many of these problems. This report discusses the feasibility and processes necessary to utilize photogrammetric techniques and photogrammetric software in order to be able to gather metric data from softcopy three-dimensional images. A non-metric 35-mm camera, scanner and software system are used to generate color stereo images from which metric data can be retrieved. Our study indicates that such a system can yield measured results from the images only that are well within an acceptable range of error. These results demonstrate the great potential of photogrammetry and modern technology for archiving images, collecting measurements and analyzing artifacts that might not physically be available for study in the future. In addition it suggests consideration of a new approach to the distribution or publication of information about collections or objects. This would involve the distribution of stereo digital imagery, on CD ROM or on the Internet. Researchers who desire detailed measurements of any illustrated object could readily obtain it from the imagery alone.

This research was made possible through Grant MT-0424-4-NC-22 from the National Center for Preservation Technology and Training (NCPTT), and through the use of softbench photogrammetry equipment and software provided by the Intergraph Corporation to the Center for Advanced Spatial Technologies.

 

Introduction


For as long as institutions and individuals have been collecting and storing prehistoric and historic materials they have struggled to find and implement a good, usable, reliable, and transferable method for archiving and utilizing their collections for research.

 

Objective


This research project looked at the feasibility of utilizing photogrammetric techniques and software systems in order to gather metric data from stereo pairs of standard 35mm photographs.

 

Some Potential Areas of Application

 

  • NAGPRA Requirements
    Analysis can be done even after the artifacts are no longer available.
  • Field Work Abroad
    Useful when the artifacts cannot be transported to the lab for analysis and analysis in the field is not possible.
  • Collection Comparison
    Artifact collections can be accurately compared without the need for travel to the collections or the shipping of valuable artifacts.
  • Teaching Tool
    Digital stereo images offer a realistic mean to view a wide variety of artifacts.

 

 

 

 

 

 

 

 

 

Our Method

 Step 1. The objects are placed in a 3-D control field  Step 2. Stereo photographs are taken

 

Step 3. The photos are scanned and processed photogrammetrically Step 4. Three-dimensional information is extracted

 

 

Conclusion

The method and results shown above are believed to be adequate for many archaeological purposes when dealing with artifacts or bones. This method allows one to archive high resolution color images with the ability to collect accurate 3-D metric data from those images. With the rapid reduction in hardware and software cost and the increase in power and storage capabilities, we suggest that this method is one way of dealing with the pressing needs of collection, recordation, and utilization.