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.