THE ROLE OF AERIAL SURVEYS IN HIGHWAY ENGINEERING 
William T. Pryor, Chief of Aerial Surveys Branch, 
Highway Standards Division, Bureau of Public Roads, 
U. S. Department of Commerce, 
Washington, D. C. 
(Paper for the Ninth Congress of the International 
Society for Photogrammetry, London, England, 
September 5-17, 1960) 
SYNOPSIS 
Historically, the 1890's was the decade in which highways and photogram- 
metry received their separate, distinct motivations on a concerted-effort 
basis. Into the 1920's both were still progressing separately. Photogram- 
metry was getting its impetus from aircraft, aerial cameras, and improved 
stereoinstruments, and in bringing aerial surveys into effectiveness. High- 
ways were getting their impetus from the rapid increases in motor vehicles 
and better construction equipment. By the 1940's, when highways and aerial 
surveys were joined together effectively on a mutually augmenting and benefit- 
ing basis, both were well advanced. Highway engineering had many mounting, 
complex, and interrelated problems arising from traffic, land use, and topog- 
raphy. Aerial surveys for highways had become the obtainment and use in the 
solution of highway engineering problems of aerial photographs and of maps 
compiled and dimensions measured by photogrammetric methods. By 1956, aerial 
surveys were complemented by electronic methods of computation and the fol- 
lowing year by electronic methods of measuring distances on the ground. 
Modern aerial surveys are now the competent and economical means by which the 
specialists on the highway team may obtain needed qualitative information and 
dimensional data, when and where required. Aerial surveys fit perfectly into 
the patterns of sequential performance, on a scheduled basis, associated with 
teamwork requirements, and enable each member of the team to get much more 
done during each usual working day. Successes, and assurances of continuing 
success, can be ascribed to the effectiveness and efficiency attainable from 
the use of aerial surveys. 
Aerial surveys are employed in varying degrees of detail, emphasis, scope, 
and success by highway departments, governmental agencies, and consultant 
engineering firms engaged in highway engineering and construction in the 
United States. The most extensive use of aerial surveys is in preliminary 
engineering--the series of coordinated stages in which the creative work is 
professionally achieved. Once the preliminary engineering is accomplished, 
results serve as detailed guides throughout highway construction and subsequent 
engineering stages. Preliminary engineering includes planning, and the four 
stages of highway location surveys, namely: reconnaissance survey of area, 
reconnaissance survey of alternate routes, preliminary survey of the selected 
and approved route whether by direct or indirect procedures, and the location 
survey. 
Electronic computation systems enable highway engineers to store in digital 
form the dimensional data obtained photogrammetrically regarding topography and 
property. Once the essential dimensional data and basic design criteria are 
suitably recorded, converted into computer language, and combined by appropri- 
ate programing, all needed quantitative determinations are accomplished quickly. 
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