(7,900 m) has increased from 10 percent in FY 1972 to 80 percent in 
FY 1975. The primary uses of high-altitude photographs are for 
aerotriangulation and preparation of orthophotoquads. 
An Itek Visual Edge Match Comparator has been installed as 
the basis of quality control for aerial photography acquired under 
contract, and for all subsequent photographic processing. 
On April 1, 1973, the calibration services and associated 
equipment for aerial cameras and lenses of the National Bureau of 
Standards (NBS) were transferred to the USGS. All equipment has been 
moved to the USGS National Center at Reston, Va., to form one of the 
most complete facilities in the United States. During the transition 
period, a number of modifications were made to increase the accuracy 
and versatility of both NBS and USGS calibration instruments. 
A new method of coordinate refinement for radial lens dis- 
tortion has been developed. Corrections are applied according to 
the grid location of the point rather than the radial distance from 
the point of autocollimation. This allows corrections for asymmetrical 
and irregular distortion and corrections for non-flatness of the magazine 
platen. 
3. Research projects in aerotriangulation included: 
a. Utilization of superwide-angle photographs to 
establish control for 1:24,000-scale topographic 
maps. 
b. Application of high altitude (1:80,000 scale) quad- 
centered photographs and semianalytical aerotriangulation 
methods to photogrammetrically establish vertical control 
for lower altitude compilation photos. 
c. Comparative evaluation of four different semianalytical 
aerotriangulation methods. 
d. Comparative evaluation of five different fully 
analytical aerotriangulation methods. 
4. The development of a Digital Cartographic Data Base was 
initiated. The primary objective is to make map information available 
in digital form for various kinds of analytical studies; the secondary 
objective is to automate some of the cartographic operations. 
A pilot project was conducted with Rome Air Development Center 
to evaluate the technical problems of deriving digital data from the 
stereomodel in the AS-11B-1 analytical stereoplotter and generating 
graphics from the data. 
-54- 
€}