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PHOTOGRAMMETRIC ENGINEERING
processed and stored for use in direct conver
sion of a digital photo to an orthophoto. The
contour tape with rectification and relief dis
placement data is converted to digitized
orthophoto data. This data is moved once
directly to its ortho-corrected position with a
minimum number of data shifts. The output
tape produced then contains the digitized
orthophoto data ready for printout on film or
diapositive, using the digital printing system.
This program is complete and will work with
rectified or (when available) with unrectified
photos, using tabulated shift data.
System Configuration
EQUIPMENT
The Digital Automatic Map Compilation
(DAMC) system is built around an IBM 7094
(Figure 3) Data Processing Unit (other proc
essors of comparable power could be used)
and the experimental DAMC photo-digitizer
(Figure l).The photo-digitizer consists of two
major sections:
1. The Magnetic Tape Units and Mag
netic Tape Adapter Unit (TAU).
Abstract: Automatic map compilation using digital techniques is progressing
at IBM in Kingston, N. Y. These advances represent over four years of re
search and development, supported primarily by the United States Army,
GIMRADA, Ft. Belvoir, Va., and IBM. Other agencies have supplemented
this effort in collateral application areas.
Experimental systems have been developed that are capable of digitizing and
processing photographic data of various quality levels, ranging from TV-satel
lite, X-ray, and radar-camera quality to that obtained with aerial-reconnais
sance and precision-mapping cameras. Up to one hundred million bits of
digitizable data are scanned from a stereo photo and recorded on magnetic
tapes for data processing purposes.
In the digital map compilation system, data associated with a pair of aerial
photographs are simultaneously digitized. The most important data of this
type are those concerned with control, obtained from ground-control surveys,
and related measurements made on an experimental photo-digitizing stereo
comparator; and other digitized data required consists of flight data, lens data,
and other instrument calibration measurements. This digitized photo and con
trol measurement data are recorded on tape for processing with a computer.
Although these operations are basically automated, human skill is required
for the stereoscopic identification and precise measurement of diapositive con
trol points. In addition, the final editing of maps to conform to topographic
practice requires the skill of expert cartographers.
A series of systems test procedures was
generated to perform an evaluation of both
the DAMC sequential and predictive systems.
The procedures, either in the form of a meas
urement or a computer program, measured
the effects of each process of the compilation
system and the total system capability of
producing contour manuscripts. Test proce
dures were developed to:
Compute the C-factor (vertical accuracy).
Compute horizontal accuracies.
Measure residual y-parallax in rectified
photographs.
Compute the spot placement error in the
scanner with computer-generated grids.
Verify the rectification process with digital
checks.
Measure operating time.
2. DAMC scanner-printer combined with
a WILD STK-1 stereocomparator.
The tape units serve as storage media for
computer input and output data. The TAU,
in addition to serving as an interface, pro
vides timing pulses and synchronization
logic for the entire system. The scanner-
printer unit has two functions:
1. To convert photographic image infor-
ihation to digital information in stand
ard IBM tape format (accomplished in
the Scan Mode).
2. To convert digital data stored on mag
netic tape to photographic image in
formation (accomplished in the Record,
i.e., Print Mode).
Since the quality of maps compiled by the