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INTRODUCTION
Archeologists and historical geographers are concerned with the discovery,
study, and evaluation of past cultures and environments. In arid climates,
the detection and delineation of archeological sites are relatively simple,
especially where vegetation is sparse or absent. By contrast, detection may
be extremely difficult in high-rainfall regions, e.g., tropical forests.
Potential sites may not only be obscured by vegetation, but their ground
scale alone may render them almost invisible to terrestrial observers. The
vertical perspective afforded by aerial imagery thus provides a new dimension
in the search for and delineation of archeological sites. And even when such
sites are not clearly discernible, possible or probable locales for detailed
ground exploration may be outlined by photographic or image analysis of envi
ronmental and microenvironmental zones.
Site detection may be accomplished by visual aerial reconnaissance or by
employing various remote sensors such as aerial photography, infrared scanners,
and microwave (radar) imagery. This brief review paper concentrates on the
applications of vertical aerial photography and infrared imagery.
HISTORICAL HIGHLIGHTS
Early Developments
One of the first practical applications of aerial archeology was demonstra
ted in 1922 by Englishman O.G.S. Crawford, who utilized shadow marks, soil
marks, and crop marks to delineate probable sites in the United Kingdom. His
successes are exemplified by the fact that he discovered more Celtic, Roman, and
"stonehenge" sites in one year than had previously been found during 100 years
of ground reconnaissance. This work firmly established aerial techniques for
archeological exploration in England.
Crawford's subsequent investigations spread to Europe, the Mediterranean
region, and eventually to the Americas in the late 1920's. In spite of notable
successes, however, aerial techniques were still quite limited during this
period because of shortages in trained personnel and the reluctant acceptance
of this new methodology by individuals and institutions that were in a position
to support and utilize the results of significant discoveries.
The 1930's saw a period of little or no expansion in aerial archeology.
However, a strong upsurge of interest developed after World War II because
of improved cameras, film emulsions, aircraft, and the large numbers of persons
who returned with wartime training in airphoto interpretation and aerial
reconnaissance techniques.
