EN
DOCUMENTATION AND VIRTUAL MODELING OF ARCHAEOLOGICAL SITES
USING A NON-METRIC
EXTREME WIDE-ANGLE LENS CAMERA
V. Arias*, T. R. Kuntz", H. Richards*, R. P. Watson b J. van der Elst?
* Dept. of Anthropology, University of New Mexico, Albuquerque, NM, USA - (arias, heathmr, jvdelst)@unm.edu
? Earth Data Analysis Center, University of New Mexico, Albuquerque, NM, USA - tera@unm.edu
? Dept. of Geography, University of New Mexico, Albuquerque, NM, USA — rwatson@unm.edu
KEY WORDS: Archaeology, Documentation, Recording, Monitoring, Change Detection, Reconstruction, Modelling, Non-Metric
ABSTRACT:
Documentation of cultural heritage sites can provide data and records for continuing research, analysis, monitoring, and change
detection. Digital documentation allows computational analysis as well as archival recording of objects and sites. It provides a non-
destructive approach to artifact or site mapping and measurement. Virtual models of cultural sites can be created from digital
imagery, using widely available non-metric digital cameras and video recorders. Software, such as PhotoModeler® allows the
construction of three-dimensional virtual modeling of objects, sites, and rooms by using multiple digital photographs. Methods for
constructing virtual models currently require multiple photos from varying angles to provide sufficient ground control points as well
as ample coverage of the site. Use of an extreme wide-angle lens camera, such as the Nikon fish eye lens, can overcome the need
for numerous pictures and allows the capture of more information per image. This can speed the process of documentation while
also providing more coverage. Wide-angle lenses have not been previously used due to the difficulty in registering the extreme
distortion on the edges of the lenses. A project was undertaken to calibrate such a lens and to test its effectiveness in capturing
images for virtual reconstruction using PhotoModeler software. The lens used was a Nikon fish-eye lens, mounted on a Nikon
Coolpix camera. Two sites were selected for the test. The first was the interior of a modern building with a large three-story atrium.
This site was chosen to initially calibrate the camera and lens for the software. The second site selected was the Salinas Pueblo
Missions National Monument, a complex of archaeological sites used to test the effectiveness of the camera, lens, and PhotoModeler
software in a cultural heritage site preservation application.
1. INTRODUCTION
An experiment with digital photography and the use of an
extreme wide-angle lens was conducted on two sites to test the
effectiveness of documenting and recording cultural heritage
sites. Archaeological sites are subject to damage, erosion, or
loss to modern construction. An inexpensive and expedient
method for recording these sites would be highly useful,
practical and would mean more extensive documentation.
Current developments in laser technology offer outstanding
results in measuring and recording sites, but the high cost and
necessary technical skill leave this as an unpractical and often
impossible alternative. ^ Traditional methods of recording
require large amounts of time and personnel. The methods
utilized in this project offer a more cost effective approach that
requires relatively little effort and few resources. The
experiment conducted in this paper began with the intention of
providing the ability to document the interior of large buildings
with a minimal amount of digital images taken with a
moderately priced digital camera, and using these images to
build three-dimensional models of the areas visited. This idea
was then extended to recording cultural heritage sites, and by
upgrading the camera and lenses to provide greater coverage
and greater resolution, accurate models could be generated with
the integration of photogrammetric software.
The initial experiment involved the interior of a modern
building with a large, three-story atrium, providing a challenge
to record its very high, vertical walls. The second site chosen
was an actual archaeological site with a similar shape and size.
The cultural heritage site that was recorded was the Quarai
Mission church of the Salinas Pueblo Complex, a National Park
Site located somewhat centrally in the state of New Mexico.
1.1 Technology Background
Cultural heritage sites are numerous, and the need for efficient
documentation is essential in the race against site destruction
due to development, erosion, and excavation. Close-range
remote sensing methods for documentation have included such
means as drawings, photography, close-range hardcopy and
softcopy stereo-photogrammetry, and laser based LiDAR
sensing. Both hardcopy and softcopy photogrammetry have
been employed successfully to document cultural features
(Turpin, 1979; Cooper, 2002), but the nature of large sites can
make a project more challenging and time-consuming. Though
LiDAR is proving to be a very fast and accurate alternative for
site documentation, it is also extremely expensive. Many
cultural sites will be excluded from this process because of a
lack of funds. The digital photogrammetry approach offered
here involves the use of an extreme-wide angle lens that will
allow the capture of larger surfaces of area eliminating the need
for copious amounts of photographs, cutting the time necessary
to photograph the site and process the images. This approach
requires relatively low cost equipment and minimal person-
hours providing a comprehensive, economic alternative.
1.2 Background of the Archaeological Project Site
The cultural heritage site chosen for this project was the Quarai
ruins of the Salinas Pueblo Missions National Monument. This
monument consists of four pueblo ruins located within an 1.1 10
acre park area. The Quarai pueblo ruins show an carly
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