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AERIAL PHOTO INTERPRETATION IN HIGHWAY AND RAILROAD
ENGINEERING
Wilbur H. Simonson, U.S. Bureau of Public Roads.
Introduction.
In order to obtain information on how and to what extent photo interpre-
tation is being used in highway and railroad engineering, a questionnaire was
prepared and sent to various state highway departments and individuals in the
United States. This report is a summary of the actual replies received. There
is, however, a wider use of aerial photo interpretation than covered by these
replies. Undoubtedly, some of the states not covered in this report are using
aerial photography in highway work. We know also that air photo interpreta-
tion is being used in highway engineering in the District of Columbia, and in
the Territories of Alaska, Hawaii, Puerto Rico, and the Virgin Islands.
Analysis of the replies brings out several interesting observations:
1. All but one of the states from which replies were received border either the
Great Lakes, the Atlantic, the Gulf, or the Pacific. In general, the majority
of these are the more populous and congested states in which highway prob-
lems are likely to be more difficult and complex.
2. The Great Lakes states use photo interpretation in more different ways,
apparently, than the states in any other section of the country.
3. Photo interpretation as a means of studying geologic and soil patterns and
locating roadbuilding materials seems to be practiced more in the glaciated
states of the North than in other sections.
4. Without exception, the states report that a saving of time, manpower, and
money is accomplished by the use of photo interpretation.
5. There is general agreement that the use of photo interpretation has increased
steadily and that its future possibilities are great.
Summary of replies to questionnaire.
The principal points submitted in the answers to the 11 questions on the
use of air photo interpretation in highway engineering are recorded.
1. QuEsTION: “What are the specific objectives of photo interpretations?"
Answers.
(1) Location of road-building materials such as rock, sand, and gravel; also
quarry and borrow sites.
(2) Study of land forms (topography) and land use (culture).
(a) Determination of drainageways, ground water, and size and charac-
ter of drainage areas.
(b) Location of centerline in rough terrain.
(c) Preliminary route or reconnaissance surveys, particularly in inac-
cessible areas.
(d) Location of highways through urban areas.
(e) Location of sites for structures (bridges, grade separations, etc.).
