On page 15-5, a call was made for users of the Tutorial (on the Internet or with the CD-ROM) to contribute material and illustrations from any GIS study they have made which would exemplify how remote sensing plays a role. On this page, we are pleased to add a GIS study from a respondee who has earlier produced an award-winning Internet site. Dr. Scott Madry and his team of associates have for many years been conducting a research project into locating archaeological ruins in a part of the Province of Burgundy in France. In recent years they have used a combination of SPOT and radar imagery together with multi-layered GIS analysis to help in finding ancient ruins such as hill forts in the rolling terrain around the Arroux River near Autun, south of Dijon, France. Part of their approach is to derive line-of-sight maps that pinpoint favorable higher locations where these forts may once have been built but are now eroded down or dismantled so as to escape ready visual detection. Remote sensing helps to disclose patterns that may be structure foundations. This add-on page produced by Dr. Madry (see the Overview for his biography) summarizes the results of their fascinating study.
AN INTEGRATED GIS/REMOTE SENSING CASE STUDY IN FRANCE
Guest Writer: Dr. Scott Madry
Another case study can show the integration of GIS and various types of remote sensing data for a rather unusual application, archaeology. This research project is a long-term analysis of the application of Geomatics to study the interaction between different cultures and the landscape over time in Burgundy, France. An American interdisciplinary team has conducted research in the Arroux River Valley region of Burgundy for over two decades.
The team uses an integrative approach termed historical ecology: the multiscalar analysis of the interaction of culture and the environment over time. A period of over 2,000 years (from the Celtic Iron Age, Gallo-Roman, Medieval, to the present) is being analyzed. The overall goal of the research has been to understand long-term interaction between these very different cultures and the physical environment. Various remote sensing, GIS, and GPS technologies have been used to support this work, which has been conducted by Dr. Scott Madry.
This map of France shows the location of the study area circled in red.
The area of Burgundy, whose chief city is Dijon, is shown in an extract from an Atlas map; note the location of Autun.
A feel for the landscape of parts of Burgundy is provided by this ground photo.
The research area consists of the
valley of the Arroux River, a tributary of the Loire River, in the Burgundy region
of east-central France.
The study area is shown from space with this SPOT image that has been merged with DEM data to give a three-dimensional sense of relief (somewhat exaggerated); Autun is in the dark area in the upper right: The valley is located in the modern
Department of Saone-et-Loire, with the
river flowing from its headwaters in theMorvan
Mountains to the Loire along a
northeast-southwest trending line. Along the heights above the river a
series of Celtic hillforts
are located. These have figured significantly in the history of the region,
as well in the research activities. Foremost of these is Mt. Beuvray, in the
northwest corner of the study area. This impressive mountain was the site of the
great Celtic city of Bibracte, capital city of the
Aedui, the powerful Iron Age Celtic polity whose
territory was centered on the Arroux. Bibracte reportedly had a population of
over 30,000 in 52 B.C., when Julius Caesar quartered his legions there. Other,
smaller, hillforts follow the river to the south, while others follow the
opposite side of the river. The major modern city in the valley is Autun (see
photo of the ancient Roman city walls as they look today). It was founded by Julius Caesar as
Augustodunum Aedorum, home of the relocated Celtic inhabitants of Bibracte after
the Roman conquest. Caesar's
conquest of Gaul, including his time in this area, was documented in his
Gallic war commentaries "De
bello gallico commentarii".
While the region retains a mostly
rural character, there are several modern threats to cultural resources in the
region. The most serious of these are a series of gravel mines (sabliers) that
run along the banks of the river. These mines are taking much of the land
immediately adjacent to the river. The mines are destroying a large number of
archaeological resources in the area, and one aspect of the project is to locate
and document these sites before they are destroyed. Archaeologists have been using aerial prospecting and
photography since just after World War One to locate buried structure,
roads, and other features of ancient landscapes. Several archaeologists who
served as pilots in that war noticed strange circles and square patterns from the air
that were not visible on the ground. After the war they returned to these
locations to find that these were actually archaeological sites, ancient roads,
etc. Early pioneers of 'aerial archaeology' conducted the first such surveys in
Europe and the Middle East in the 1920's. Charles Lindbergh also conducted
similar surveys in Central America in the 1930's. How is it possible to see
ancient landscapes and the remains of structures that can be a thousand years
old? Faint lines and color changes
visible from the air are often invisible on the ground, and can be caused by
buried cultural remains. Aerial archaeologists refer to these as crop, soil, and
shadow marks. Crop marks
form because there can be notiecable variations in crop vigor, color, or height
when crops or natural vegetation grows over buried walls or other cultural
remains. These are called 'negative' crop marks, as
the crop is less vigorous due to the lack of moisture or root vigor caused by
the buried walls. The opposite are 'positive' crop marks,
where the crops are taller or more vigorous when growing over pits or post
holes. There is more moisture and better root growth, so the crops grow better.
These differences are heightened in times of crop stress, such as a drought. In
the major French drought of 1976 thousands of new archaeological sites were
discovered from the air. Soil differences also can be visible, such as where a
road or ditch was filled in with soil from a different place. These are called
'soil' marks. Small
variations in topography causing shadows that are visible early or late in the
day, these are called 'shadow' marks. 15-20: The aerial photo below shown a Roman Villa discovered
in 1979 during low level aerial survey for this project. This is a 'negative'
crop mark. What kind of detail of the structure can you see? Look in the upper
right portion of the photo. There is a green square, a 'positive' crop mark.
What do you think that this might be?ANSWER 15-21: The
ground photo below was taken the same day (see the person walking in the
background for scale). Can you see the outline of the structure? If you were
walking along, would you be able to tell there is a buried structure here?ANSWER An excellent source of remote
sensing information for archaeologists is archival aerial photography, the older
the better. U.S. Army Air Corps aerial recconnaissance photos of the region
dating from September 1944 were acquired from the U.S. Defense Intelligence
Agency using a Freedom of Information Act Request (FOIA). These photos were
acquired during the Allied push into the region near the end of the
Second World War. Over 200 black and white vertical aerial photos of a scale of
approximately 1:40,000 were acquired and have been manually and digitally
analyzed to search for archaeological sites, roads, etc. Numerous features have
been located and mapped. 15-22: Look at the photo below. What kind of
marks do you see? What do you think they are? ANSWER
15-23: Below are a 1944 aerial photo of Mt. Dardon
and the 1983 1:25,000 IGN map. What differences do you see?ANSWER
This project has used a variety of
modern remote sensing data. Since archaeological remains are very small,
airborne data are very useful in conjunction with satellite data. The Aries scanner system is a
French airborne digital radiometer system that was used on this project. It was
constructed by the Laboratoire de Météorologie Dynamique (CNRS, France). It has
two channels, normally set with one in the area of the visible and near
infrared, and the other in the thermal portion of the spectrum (Perisset and
Tabbagh, 1981:185). Internal calibration of the thermal scanner can provide
apparent temperature recording capability. The spatial resolution of the data is
dependent on aircraft elevation, but 1-2 meter data are typical for missions
such as ours. For this project, the ARIES scanner system was mounted in a single
engine Pilatus aircraft, and three corridors within the research area were flown
in 1987. This airborne thermal scanner image
shows the location of the Roman villa structure which has been destroyed by a
gravel mining operation (shown by a star on the image). The field is now a lake.
This is a fairly common situation in Europe, and part of the project activities
is to locate archaeological resources so that they can be studied before they
are destroyed by modern activites. 15-24: In the airborne thermal image above
can you see any patterns in any of the fields?ANSWER
A somewhat more ambiguous example appears in the image below. This is the area in the upper left of the above infrared image. The "arrow(>)" marks point to a faint but perhaps meaningful curved (arc) pattern which may also be an ancient wall or some other buried structural feature. 15-25: How can thermal IR
imagery help in finding buried archaeological remains?ANSWER
The Autun project has used a variety of
satellite imagery over the years, including Landsat MSS (80 meter) and French
SPOT (20 and 10 meter) data. The SPOT data has a spatial resolution of 20 meters
for multi-spectral data, which records information in three bands of the
spectrum, and a 10 meter spatial resolution for a panchromatic band. The
resolution of these images available from space can provide significant
improvements in the utility of these data for regional archaeological and
environmental applications, especially (as in France) where the field size is
very small. Here is a false color SPOT image that includes part of the research area. In this image, Autun is at the upper right and Mt. Beauvrag at the upper left.
Accurate modern landcover maps were produced using SPOT satellite
imagery. The upper part of this next image/classification corresponds to the above SPOT scene; look for the blue horseshoe pattern to fit it in.
Canadian RADARSAT-1 satellite
imagery has been acquired for the region on 4 November, 1998, shown below. With a spatial
resolution of 8 meters, this system is different from SPOT or Landsat in that it
is an active radar system that sends its own burst of electromagnetic radiation
down to the ground which bounces off the surface and recorded by the
satellite. This system can operate day or night and through cloud cover. It
provides a different and new way of visualizing the area.
The first scene below shows the area around Autun. Below it is another Radarsat image that illustrates the hilly topography in parts of the study area. The GIS data base covers an area of about 30 by 60 km,
covering the majority of the Arroux River Valley and its immediate environs. The
current basic raster layers of the GIS data base include: elevation (generated
from the French digital elevation data), aspect (derived from the digital
elevation data), slope (derived from the digital elevation data), SPOT images (20
meter false color infrared), SPOT images (10 meter panchromatic), land use/land
cover maps (derived from Spot image data), geology (generated from 1:80,000
geology map of the upper 2/3 part of the region), faults (from the same 1:80,000
geology map), hydrology (from the three 1:50,000 topo maps), modern roads (from
the three 1:50,000 topo maps), ancient roads (from project information and old
maps), known Celtic hillforts (from project information and old maps) data layers
showing different distance categories, or buffer zones, from roads, streams,
faults, archaeological sites, hillforts, and ancient roads (also generated
from the data above). Additional data have recently been added that were derived
from the 1:25,000 maps.
Two of the thematic maps listed above are of special utility in the GIS analysis described below. On the left is a map of the Celtic road network developed in or after Roman times. On the right is a map of known hill forts of the time. These are helpful in calculating distance from any vantage point to specific features. An original year 1659 map of the region and two 1759 maps of the research area were digitized using 4,000 by 4,000 digital CCD array device that converts maps or photographs into digital format. The 1659 map
which was scanned from the original, entered into the GIS, georeferenced, and entered into the GIS system as a data layer like any other. This map is quite general in its spatial accuracy, but it is the oldest map yet found that covers
the research area. Here is part of this map: Two
1759 maps were also scanned into the system and patched together to make a
single data layer. Here is the Cassini map centered around Mt.
Dardon. It clearly shows the roads, rivers, topography, and every individual
house and structure.
These 1759 maps were produced for the famous Cassini
triangulation survey of France conducted in the mid 1700's. This massive work
took three generations of the Cassini family to complete, and was the first
accurate survey of an entire nation using modern surveying and mapping
techniques. Reproductions of the maps are available for all of France from the
Institut Geographique National in Paris. These historic maps are extremely
detailed and accurate, much more so than the older map we possess created 100
years before it. The
Cassini maps provide us with the oldest, reasonably accurate, record of the
location of roads, bridges, towns, and villages of the area. It also shows
information about the vegetation and land-cover of the area at that time. The
maps contain an astounding level of detail, and have been digitized to represent
a series of GIS layers representing the cultural and environmental makeup of the
area at that time. One of the more interesting results
from the GIS analysis was the line-of-site analysis (Madry and Rakos 1996). This
GIS technique allows one to determine what parts of the landscape are visible
from any given location. The research demonstrated that the old Celtic road
network connecting the hillforts of the area tended to follow within the
line-of-sight of the hillforts, rather than take more direct paths (as
originally proposed in Madry and Crumley 1990). We have run the same
line-of-site analysis from four locations on each of the known Celtic hillforts
in the research area . These four line-of-site maps for each hillfort were then
combined to generate a map of complete inter-visibility from each entire
hillfort, assuming that the forts were manned by watchers from each of the four
"corners" of the ramparts. An eye height of 5 meters above the terrain was used,
assuming that towers of just over 3 meters height were strategically located
around the ramparts (and that the eye level was just under 2 meters above that
height).
These individual line-of-site maps are combined to produce the map below
which shows (in red) the total portion of the research area and each ground transect that
is within line-of-site of each hillfort, and for the total network of hillforts
in the region. This analysis shows that the Celtic roads definitely tend
to follow paths that stay within the view of the hillforts, even if they are
less direct or require a steeper climb. Additional work was done to model the
location of Celtic and Gallo-Roman roads where the exact location
of segments is not known. Site location modeling is a useful
GIS product for archaeologists who wish to locate and protect unknown cultural
resources. It allows us to model where archaeological sites of a given period
may be located, based on the known site locations and various
environmental and cultural data in the GIS. Predictive models were developed on
this project using site data generated from field surveys conducted in 1978 and
1979. A model based on environmental and cultural data was created that
accounts for 78.9% (45 of 57) of all Gallo-Roman sites in only 29.2% of the
total area that was field surveyed. The same model also includes 69.2% (36 of
52) of the Iron Age sites and 80.3% (49 of 61) of the Medieval period sites
located in the field survey. This model was then generalized to include a much
larger area surrounding the transects (4.7 times as large). New layers in the
GIS containing these locations were produced along with new maps showing the areas with
the highest probability of site locations. These areas of higher
probability of archaeological sites have a high correlation with areas that are
threatened by current gravel mining activities in the area. Current
research involves analysis of aerial photography and site surveys using GPS in
the areas predicted to have higher site potential by the predictive models.
Coordinates of high probabililty areas are entered into GPS units, which are
used in the field to search for the exact location of the archaeological sites.
GPS receivers are also used in the aircraft while conducting aerial prospecting
and photography. The GPS allows us to locate our position and the location of
the photographs much easier than looking on maps for individual fields while the
aircraft is banking and turning. These Roman sites tend to cluster along the rivers in flat bottomlands, and also along the Roman roads. Celtic living sites tend to be more in uplands and near the Celtic
hillforts on the hilltops. The largest single area of high probability is the
area shown below, next to the river, where the Roman villa was located and later
destroyed. The gravel operations continue to work in the area, and researchers
are trying to locate additional sites using these techniques before they are
destroyed.
This project has used a variety of
visualization tools to assist in better understanding both the data and the
region. New technologies allow us to view our data in interesting
ways from the laboratory when it is not possible to be in the field. For example, we can "fly" through
the study area and look at different GIS layers draped over the terrain. First
we need a digital elevation model (DEM) showing the topography of the region.
For this project this was generated from the French 1:25,000 scale topographic
maps. Shown on the left above is the
gray-scale DEM image of the Arroux river valley. Lower elevations along the river are shown in black, shading to white which
represents the highest terrain in the region, including the site of the
hillforts. From this a slope steepness map, seen on the right, can be derived using colors to indicate small intervals of slope values in degrees. These data can be displayed in several ways: one is the SPOT image of the study area with topographic effects superimposed, as we saw near the top of this page. Drawing upon an appropriate topographic rendition, we can create perspective views that ultimately can be combined to produce a 3-D fly-through of
the valley (described below), which shows the region in three dimensions as we fly up the river. We may choose to overlay any individual or combination of GIS data layers in these views. As seen from an oblique aerial perspective, the GIS scene for an instant might look like this: To generate the fly-by, we have applied a program that uses input data such as we have created to generate a movie-like run through the scene. Quicktime Virtual Reality
(QTVR) lets us pan and zoom interactively on our computer (or over the
web) to see the actual view from given locations in the study area. This is very
useful in determining the accuracy of Line of Sight GIS computations, and also
in allowing people to experience a virtual visit to the research area on the Web. To view the
Quicktime VR movie you will need to download a free plug-in available from Apple Computer (the software runs in both Macintosh and Windows). For futher information, click on the Visualization word found on the Home Page of the Web site set up by this research team. That site also has background that supplements the overview on this Tutorial page and has the .mov file. It is your choice as to trying to download that file and run the movie. Unless you already have Quicktime, that program takes up to an hour to download. The visualization is outward from the perspective centered around
the summit of the Celtic hillfort of Mt. Dardon you have seen in the images
and maps above. You can put your mouse on the image and click, then drag your
mouse to look left and right, up and down. You can also zoom in and out using
the 'shift' and 'control' keys. You can see the commanding view this hillfort
had of the surrounding terrain, and portions of the Celtic
ramparts which have survived intact.
Aerial imagery, and even more, GIS data are somewhat difficult for many people
to relate to. They are abstract and it is hard for many people to relate what
they see on the computer screen with what is actually on the ground.
Visualization tools like QTVR allow us to bridge the gap between the imagery and
reality, providing the ability for us to 'visit' the research area and compare
the actual landscape with what we see on the various images and GIS
layers.
The summit of Mt. Dardon at
Sunset. This project has used a variety of
tools to study the regional archaeological patterns of a large area in France.
Particular emphasis has been placed on finding archaeological sites and then
predicting the location of unknown sites before they can be destroyed by modern
land use practices. It is the combination of new technologies and techniques,
such as aerial photography, GIS, GPS, remote sensing, and visualization, that
provides the greatest value to the researchers. Work on this project is
continuing. Time's patterns pieced
An article
for the UNC Endeavors magazine about this project Satellite remote sensing for archaeology
Aerial archaeology An excellent overview of aerial
archaeology by one of the best sources GRASS visualization Includes links to other visualization programs USGS GIS Provides an overview of GIS Aerial archive links (U. Wien) An rich site dealing with
archaeological topics, including use of aerial and satellite imagery Line-of-sight and Cost Surface Techniques
for Regional Archaeological Research in the Arroux River Valley, (with L.
Rakos), 1996, in: New Methods, Old Problems: Geographic Information Systems in
Modern Archaeological Research, edited by H. D.G. Maschner. Center for
Archaeological Investigations, Occasional Paper no. 23, pp. 104-126.
Applications of Digital Terrain Data, Archival
Maps, and Historical Aerial Photographs for Regional Archaeological Analysis,
(with R. Wincek), April 2,
1995, paper presented at the 23rd annual meeting of the Computer
Applications in Archaeology conference, Leiden, the Netherlands,
Un Emploe des Systemes de Teledetection et
d'information Geographique dans une Analyse Regionale de Repartition Spatiales
Archaeologiques, 1991 In: Archeologues et Ordinateurs, Lettres d'Information du
Centre de Recherches Archeologiques. 17:1-11. Paris: Centre Nationale de la
Recherche Scientifique.
An Application of Remote Sensing and GIS in
a Regional Archaeological Survey (with Carole L. Crumley), 1990. in Interpreting
Space: GIS and Archaeology, K. Allen, S. Green, and E. Zubrow, eds. Taylor
& Francis, London.
Application des Systemes d'Information
Geographique Informatiseé et de Teledetection en Releve Archeologique
Regionale Bourgogne, France, et Caroline du Nord, USA., 1990 in Journees d'Etude
Internationales: Teledetection et Cartographie Thematique en Archeologie,
Valbonne, France CNRS/CRA.
Remote Sensing and GIS Analysis in Large
Scale Survey Design in North Mississippi, Jay Johnson, S. Madry, and T.
Sever, Vol. 7, Number 2, Winter 1988, pp. 124-131 Southeastern
Archaeology.
Remote Sensing in a Temperate Regional
Archaeological Survey in France, 1987 in Regional Dynamics: Southern Burgundy from
the Iron Age to the Present, edited by C. L. Crumley and W. H.
Marquardt-published by Academic Press.
Téledetection,(Remote Sensing), 1986, in Vol. No.
56 pp. 2-6. in Echos Du Passé, Revue Periodique de l'Association Les Amis Du
Dardon, Gueugnon, France.
La Grenouilliers Perdue, 1985, Vol l. No. 54. in
Echos Du Passé, Revue Periodique de l'Association Les Amis Du Dardon,
Gueugnon, France with Dr. Carole L. Crumley. Remote Sensing in Archaeology, in
Archaeology, May-June, l983 (l8-l9). Reprinted in French in Echos du Passé,
Bulletin du Les Amis du Dardon, Gueugnon, France, l985.
Primary Author: Dr. Scott
Madry email: madry@informatics.orgAerial Photography
Project Historic Aerial Photography
Modern Remote Sensing Data
SPOT Imagery
Radarsat Imagery
GIS Analysis: The Project GIS Data Base
Historic Map Digitization
GIS Analysis: Line-Of-Sight Determination
Predictive Modeling
Visualization and Simulation
Conclusions
For more information off the Internet:
Informatics International, Inc. and Dept. of Anthropology,
UNC-CH