Building Three-Dimensional Models of
Archaeological Sites by Creating a
Specialized GIS for Archaeologists
John R. Samuelsen
CIS4914, Senior Project
Department of CISE
University of Florida
Advisor: Dr. Benjamin C. Lok, email: lok@cise.ufl.edu
Department of CISE
University of Florida, Gainesville, FL 32611
Date of Talk: 14 April 2004
Abstract
Current commercial Geographic Information Systems (GIS) are centered on twodimensional viewing and editing of data. Programs that have three-dimensional viewing
are limited and like most GIS are made primarily for geographers. Previous research
projects have created highly accurate 3D representations of archaeological sites. While
these projects are valuable to the archaeologists working on the site that was modeled,
they will not model any other sites. Archaeologists lack programs that are designed to
represent any site in 3D while incorporating the most common and important
archaeological data. Therefore, a specialized GIS for archaeologists must be created that
provides many 3D views for archaeological data and models any site. A GIS called “Site
Explorer” shows 3D views for any site and incorporates important archaeological data
such as test units and stratigraphy.
Keywords: Scientific Visualization, Archaeological Data Analysis, Geographic
Information Systems, Virtual Environments
1.
Introduction
As graphical representations become more accurate, scientific fields such as
archaeology are expanding to include new ways of analyzing and viewing data.
Archaeologists make use of current programs and Geographic Information Systems (GIS)
to view and analyze data, but they do not have a program which incorporates features that
aid archaeological research. Since archaeology is a destructive science, sites are changed
forever by the study itself and potentially important data is lost. Can a GIS be created to
help preserve sites and their data, while allowing for research with the way the data is
viewed? ESRI’s program ArcSceneTM [3] allows for data storage and viewing of the data
in 3D. Many researchers that combine computer graphics and archaeological research
have implemented their own models of sites and have developed new ways to make the
models more accurate. The virtual environments which have been created are extremely
accurate, but the programs are site specific. Commercial programs like ArcSceneTM
contribute to archaeological research, but are specialized for geographers. Therefore, a
specialized GIS for archaeologists using the latest in three-dimensional graphics, which
incorporates virtual environments, will help archaeological research. The GIS should
take the best from the commercial and the research oriented designs by having multiple
ways to view the archaeological data, keeping the viewing of data accurate, and allowing
the implementation of multiple sites’ models.
2.
Problem Domain
One major question that archaeologists ask about a site is, "How did the people
who lived here years ago see the site?" The analysis of what can be seen from a certain
point is called viewshed analysis. In order to get an accurate view for the analysis, a
virtual environment with a first person view that is analogous to a person walking on the
surface of the site is preferable. There are many other questions about the way that the
data is viewed. Another problem dealing with the visualization of archaeological data is
the viewing of stratigraphy in test units. Unfortunately, test units are not supported by
commercial GIS. Archaeologists currently use 2D models for questions like this and the
3D models that are used often do not have sufficient first person views.
3.
Previous Work
There are very informative studies which have been done recently dealing with
viewing archaeological data. There are two very different types of data viewers that are
being developed. One is the commercial GIS, ESRI’s ArcSceneTM [3]. It uses OpenGL
to display graphics and has many functions that allow for the manipulation of data in a
3D view. This program uses much of the newest technology available and it is
compatible with all of ESRI’s other programs such as ArcViewTM and ArcCatalogTM.
The program is made mainly for geographers and geo-scientists. Although this program
works well for those scientists, it is limiting for archaeologists as it does not implement
the most common archaeological data structures, such as test units. Another problem
with ArcSceneTM is the inability to display vertical textures. Satellite imagery is
displayed horizontally on the sites surface. In order to put textures on a vertical wall, a
different method is needed. These vertical textures are necessary for archaeologists to
model walls of test units and walls of other types of excavations which have some of the
most important data on them, namely, stratigraphy. The third problem is that it is
impossible to view the data in a virtual environment or as if the viewer is actually at the
site. The only first person view that exits for this program is a flying movement view,
which does not help archaeologists move or see what a people would have seen as they
walked along the ground years ago.
The other type of data viewer that is being developed is the research oriented 3D
site models. Research has shown that these well-developed site models contribute to
archaeological analysis. In one study, archaeologists who studied that site evaluated the
program and its usefulness to their study of the site. This study shows that archaeologists
can find new information about old excavations done by previous archaeologists using
site specific 3D models. One archaeologist discovered that data that was thought to be
in-situ from a previous site report was actually disturbed [1]. The possibility of
incorrectly visualizing data is one reason many archaeologists are apprehensive about
using computer models. Accuracy in data viewing can be reinforced by research dealing
with the change in displaying method based on a change in time period. For example,
normal OpenGL lighting can be used to represent natural light and electrical light, but
what lighting settings would be right for an oil lamp used hundreds of years ago [2]?
Finding information to make lighting more accurate for a specific time period is of
utmost importance to archaeologists. Some research portrays active ceremonies with the
most accurate of movements and clothing style [4]. Painstakingly accurate
reconstructions of buildings for 3D modeling show the importance of accuracy [5].
These programs have many benefits; however, they show one site and one site only.
There is no way to enter new data easily as the commercial programs allow. These types
of models are informative for archaeologists working on that site, but are useless to other
archaeologists who want to make a model of their site without having to rewrite the code.
4.
Solution
In order to make a specialized GIS for archaeologists, it is necessary to include
functions and data structures that allow them to view and edit archaeological data. All
data for a specific site and time period are saved in a structure called a “layer”. Using
layers allows for multiple sites or multiple time periods for the same site to be displayed
simultaneously. A layer is made up of the following 6 possible data types: points,
triangles (mesh), texture, sound, trees, and test units. The first and most simplistic data
type is the point. The points are 3D and are used to represent data obtained from an
electronic transit, a surveying instrument consisting of a small telescope mounted on a
tripod, used at the site. A list of points is loaded by a text file listing them. These points
are then represented in 3D in the view. The points can then be used to make a triangle
mesh or a Triangular Irregular Network (TIN) by using Delaunay Triangulation. The
mesh that is created is a full 3D model of the site’s topography. This mesh can be saved
to a file for later use. Most settings and all data can be saved to a file. Textures such as
satellite imagery can be loaded from a file and zoomed, moved, and rotated so that the
points link up with the correct part of the 3D model. In this way, a 3D model of an
archaeological site with satellite accuracy can be created quickly. If the original points
are taken with an electronic transit that outputs the data points in an appropriate format,
the site model can be updated quickly and efficiently while on site. This allows
archaeologists to analyze the topography and aids them in deciding where to or where not
to dig next. Since much of the analysis can take place in the lab years after the
excavation, updating the model while in the field can help organize data and give the
archaeologists a head start on their analysis of the site. Sound and trees emphasize the
virtual environment possibilities and also give the user a size reference. Test units are
especially important because each side has a texture that can be moved or stretched to
match up with the corners of the side. Hence, a 3D model of the test unit is created
showing the stratigraphy as it was when the site was excavated.
Multiple views are necessary to allow for better analysis and viewing of data.
The initial view is a third person view which rotates around the center of the site. The
center of rotation is movable. “Virtual mode” zooms into a first person view that allows
the viewer to walk on the surface of the site as if they were presently at the site. The user
can change the “world size”, or make the site larger or smaller, so that the site’s size
appears correct. The clipping area, or “sky distance”, can also be changed by the user so
that objects closer or farther away are excluded. Movement speed through the site is also
changeable so the user can run, walk, or move inch by inch. With these view and
movement options, the user has full control over the environment and its properties.
When the user saves the file, these settings are also saved. The user can switch between
these views without changing any of the data. While in virtual mode, rather than walking
on the surface, the user can choose “bird mode” which is a first person view that allows
the user to appear to be flying through the site. The three types of view and movement
allow archaeologists to do viewshed analysis and give them a view that is not available
with current commercial GIS.
5.
Results
Hontoon Island is located on the St. John’s River in Northeastern Florida. During
the summer of 2003, the St. John’s Archaeological Field School excavated Hontoon
Island with Dr. Kenneth Sassaman, the head archaeologist. This site used to have two
large shell mounds created by indigenous people 6000 years ago. Today, the island only
contains small remnants of the shell mounds. The smaller one was eroded over time and
in the 1930’s both shell mounds were mined to make shell roads. Topographical points
of the island were gathered over the summer as we excavated. These points were saved
to a text file and then loaded into the program that is called “Site Explorer”. A mesh was
then created a satellite image added, and trees were added to show the island as it is in
Figure 1.
Figure 1. Hontoon Island as it was in the summer of 2003.
This view is looking toward where the larger mound used to be.
A new layer was creating using “digitize mode” and a verbal description of what
the island looked like in the 19th century. Showing both of these layers at once, the
change in topography is displayed. Previously, seeing both topographies at once was
something that could only be imagined. Also, by viewing both layers and the test units
with stratigraphy, the position of stratigraphy can be compared with where the mounds
would have been placed in the past to determine new information about the nature of the
stratigraphy. For example, this information could be used to determine if the layers of
sediment were laid down all at once or if they were laid down slowly over time. The past
view of Hontoon Island is very different than the present, as seen in Figure 2.
Figure 2. Hontoon Island as it was 6000-100 years ago.
This view is from atop the larger mound
Site Explorer must be usable by archaeologists. In order to ensure natural use by
archaeologists, the Microsoft Foundation Classes (MFC) library was used to create the
user interface. A tree view was implemented so that the data is easily viewable and so
the view of the data can be toggled easily as well. If some other user interface is used, it
may limit the usability of the program.
As intended Site Explorer will load data from any site and represent the data
accurately. The ability to travel on the surface of Hontoon Island’s past allows
archaeologists to see what the island would have looked like if they were in the past and
walking on the island. Hontoon Island’s excavation is saved in the computer. Although
excavating is a destructive process, using Site Explorer can help preserve the data that is
collected like the data shown in Figure 3.
Figure 3. This is a view of a test unit from Hontoon Island.
6.
Concluding Remarks
The creation of a GIS made specifically for archaeologists helps archaeologists to
solve problems and see their site in ways that were not possible before. Making the
program able to be used for any site increases the usability of the program.
Archaeologists can create and send a site to another person to spread information and
data.
There are many possibilities for the program in the future. Perhaps allowing
textures to be placed at any point in the test unit would allow a reconstruction of the
excavation. The incorporation of artifacts into the program could aid analysis. The
addition of artifacts can be problematic. Many archaeologists will not accept sample
artifacts to represent actual artifacts. For example, the artifact found at the site may be a
Folsom projectile point, but the closest representation is a Clovis projectile point.
Representing a Folsom projectile point by using a Clovis point could be seen as
unacceptable. One solution to this problem could be to scan in the actual projectile point
using a 3D scanner.
One disadvantage of using Site Explorer would be that it is not compatible with
programs such as ArcViewTM and ArcCatalogTM which are used very often by
archaeologists. Also, inclusion of detailed models of buildings or other objects is not
possible yet.
7.
Acknowledgements
The author would like to thank Dr. Benjamin Lok has been extremely helpful by
guiding him and keeping him focused on the important parts of the project. Dr. Kenneth
Sassaman also deserves special thanks for helping the author by introducing the idea of
building a 3D model of Hontoon Island. Dr. Sassaman supplied all the data needed to
make the model of Hontoon Island in the present and in the past.
8.
[1]
References
Acevedo, Daniel, Eileen Vote, David H. Laidlaw, and Martha S. Joukowsky.
“Archaeological Data Visualization in VR: Analysis of Lamp Finds at the
Great Temple of Petra, a Case Study”, Proceedings of IEEE Visualization
2001 (San Diego, California. October 2001).
[2]
Devlin, Kate, Alan Chambers, and Duncan Brown. “Predictive Lighting and
Perception in Archaeological Representations", AFRIGRAPH 2001, pp.
43--47 (2001).
[3]
Kennelly, Pat. "Createing Three-Dimensional Displays with ArcScene",
http://www.esri.com/news/arcuser/0103/files/3display.pdf, CW Post
Campus/Long Island University (as-of 12 Apr 2004).
[4]
Papagiannakis G., A. Foni, and N. Magnenat-Thalmann. “Real-Time Recreated
Ceremonies in VR Restituted Cultural Heritage Sites”, CIPA XIXth
International Symposium (30 September, July 2003).
[5]
Sundstedt, Veronica A High Fidelity Reconstruction of Ancient Egypt: The temple
of Kalabsha, M.S. Dissertation, University of Bristol, UK, Department of
Computer Science, (2003).
9.
Biography
John R. Samuelsen was born in Fairfax, Virginia on September 24th, 1981. He
earned an International Baccalaureate degree at Hillsborough High School in Tampa,
Florida where he lived from 1985 to 1988 and from 1989 to 2000. Upon graduation, he
sought a B.A. in Anthropology and a B.S. in Computer Science from the College of
Liberal Arts and Sciences at the University of Florida (Gainesville, FL), where he expects
to graduate on May 1st, 2004. Mr. Samuelsen intends to attend graduate school for
archaeology at the University of Arkansas starting in the fall of 2004. There he plans to
continue his interest in combining the fields of archaeology and computer science with
Dr. Fred Limp. He is proficient with C, C++, Java, MFC, and OpenGL. Mr. Samuelsen
enjoys many video games such as the Final FantasyTM series and other RPG’s. Other
interests include watching Tampa Bay Buccaneers football games and watching anime.