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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.