DIGITAL TECHNIQUES FOR MAP COMPILATION 
225 
Fig. 2. Aerial diapositive (one of a stereo pair). 
the future. The program is sufficiently com 
plete to demonstrate digital mapping feasi 
bility by producing orthophotos and contour 
overlays on these models. 
This system control program, when using 
unrectified data, will convert ground and 
interior orientation measurements (using 
resection and orientation parameters) to a set 
of tables for controlling the direct contour 
program. These tables, which can be subse 
quently expanded for optional use in the di 
rect orthophoto program, will contain rectifi 
cation shift data for all distortions, control 
points, tic markpoint locations, and symbols. 
The tables will also include secondary control 
points which define non-correlatable areas by 
the perimeters, such as built-up areas, lakes, 
bay surfaces, etc. Shift of data for final map 
projection will also be part of the program. 
In the direct contouring program, the 
digitized photo pair data are processed to re 
duce the storage of photo data to a minimum 
time and amount. The photo pair is processed 
with rectification shift data, using point cor 
relation among a set of predicted conjugate 
image points. A set of orthorcorrected paral 
laxes and elevations is produced first; then 
the contouring routine completes the pro 
gram. 
In the direct orthophoto program, a set of 
rectification and relief displacements is first 
Fig. 3. IBM 7094 Data Processing System.