Early Development 
  
Aerial surveys for highways were at first merely an aerial observation 
procedure--the flying over an area, route, or site, and gaining such infor- 
mation as could be seen and brought back in the form of handwritten and mem- 
ory notes for subsequent use. From such a beginning, aerial surveys have 
progressed through the taking of single intermittent aerial photographs with 
any available camera to the taking with a precision aerial camera and appro- 
priate use of complete stereoscopic coverage. Aerial surveys are now utilized 
in nearly every phase of each stage of highway engineering, and utilization 
gradually and ineluctably evolved through the efforts of enterprising indi- 
viduals who aspired to make possible the greatest benefits for all concerned. 
These individuals applied their initiative wisely by taking advantage of oppor- 
tunities--even creating them. They were men with persistence who realized the 
importance of their objectives, and knew how to attain them without faltering, 
despite objections, seeming failures, and unforeseen obstacles. 
Pioneers in the fields of photogrammetry and of highway engineering 
deserve full credit for their contributions in each field and for doing what- 
ever they could to combine the two professions in a mutually augmenting and 
complementing manner. Successes in both fields had their beginning in the 
1890's. Highway construction was Just beginning on an organized basis in the 
United States. At the same time, there was an increasing number of people in 
several countries who were directing their interests, talents, and efforts 
toward the development of photogrammetry as a means of using photographs taken 
from vantage points on the ground for making measurements and compiling maps. 
Since then, advancements in the fields of photogrammetry and highways contin- 
ued, simultaneously and separately, for more than thirty years. 
When the first legislation providing Federal aid to the States for high- 
way construction was put into effect in the United States in 1916, the impor- 
tance and need for a system of improved highways was recognized. This legis- 
lation established a working relationship between the States and the Federal 
Government which, over the years, has grown in scope and effectiveness through 
professional integrity, mutual confidence, and wholehearted cooperation. At 
present, the Federal-aid highway system comprises 815,000 miles. This system 
is about one-fourth of the total road and street mileage in the country, and 
includes 41,000 miles (66,000 kilometers) of Interstate highways of which 
5,800 miles (9,300 kilometers) have been constructed and over 4,300 miles 
(6,900 kilometers) are now under construction. Moreover, within the past four 
years, Federal-aid highway construction contracts have been awarded totaling 
nearly 15 billion dollars. Such figures indicate the magnitude and scope today 
of highways within a country comprising slightly more than three and one-half 
million square miles (9,065,000 square kilometers). In the year 1900 there 
were only 8,000 automobiles in the United States used mainly for recreation 
and ostentatious displays, and to begin the gradual change of our on-the-ground 
mode of transportation; today there are TO million motor vehicles performing 
&ll types of traffic services on the streets and highways. 
Although it has been about seventy years since highway construction and 
photogrammetry had their separate beginnings on a concerted-effort basis, it 
is only within the past half century that motor vehicles have been supplanting 
to & significant degree other modes of transportation on the ground. This 
began in the transportation of people for recreation and to and from work. 
There rapidly followed, on a continually increasing basis, the movement of 
goods by motor truck, especially within the past three decades. The results 
of the rapid increases, numerically, in the various motor vehicles engaged in 
all types of highway transportation are visually represented by the vast sys- 
tems of highways already constructed, and by the traffic congestion that exists, 
especially in and near cities. In looking ahead, highways are now being engi- 
neered to meet expected traffic demands.in the year 1975 of 110 million motor 
vehicles traveling upward of one trillion vehicle miles per year. The economic