GENERAL COMMENTS 
It is now no longer questioned as to whether or not photogram- 
metric instrumentation methods of surveying (using double projection 
and optical train instruments) will be adequate for making surveys to 
accomplish highway. engineering. This is so regardless of the stage in 
which aerial surveys are employed. Fortunately, accuracies can be 
varied according to need and stage of use--the less accurate, of course, 
being acceptable in the planning and reconnaissance stages and the most 
accurate being required for the design, preparation of detailed con- 
struction plans, cadastral surveying, and computation of construction 
pay quantities. Only where the ground is completely obscured by tall 
and dense vegetation need clearing contracts be awarded and the route 
corridor cleared in advance of utilizing photogrammetry to make pre- 
cision measurements and compile accurate maps in making a detailed 
survey of the ground, soils, drainage, and cultural features. 
The most significant benefit accruing from use of aerial surveys 
is the fact that a larger amount of qualitative information and more of 
the needed quantitative data are readily available for use by the 
engineers in each of their respective areas of responsibility than 
when relying solely on the usual methods of surveying on the ground. 
The savings accrue not only in reducing surveying costs; but more 
importantly in reducing the cost of rights-of-way, costs of fitting 
the highway to the topography and land use, costs of construction, 
costs of highway maintenance, and costs of vehicle operation on the 
highway.