Sensing Additional Information 
There is no reason, of course, to limit the effort to 
improve the automatic stereoperception process to 
direct improvement of the image-correlation process. 
Techniques which allow other types of information 
to be sensed and transmitted to the computer must 
also be considered. Pattern-recognition techniques are 
of particular interest in this respect, because they 
tend to automate the photointerpretation function. 
An accompanying papert describes research on a 
pattern-recognition approach which employs an auto- 
matic statistical analysis of the scanned video signals 
from the flying-spot scanners and the video correlator 
outputs and is thus directly compatible with the pre- 
sent automatic stereoperception equipment. 
A pattern-recognition system, integrated with an 
automatic stereoplotter, might provide several addi- 
tional features. One application is the automatic 
recognition of obstacles such as trees and buildings 
which produce appreciable elevation errors. A further 
step would be automatic measurement of these errors 
so that they could be compensated for within the 
computer. These techniques would do much to ex- 
tend the application of automated instruments to 
large-scale mapping. 
A pattern-recognition system might also provide 
information which would assist the computer in con- 
trolling automatic plotting of contours and profiles. 
For example, automatic recognition of open fields or 
water features might be used to provide more effec- 
tive traversing of such areas, while recognition of 
image patterns corresponding to sharp changes of 
terrain elevation or slope might be used to more care- 
fully plot these features. 
An additional application for pattern-recognition 
techniques is automatic extraction of the planimetric 
data from the photographs. These techniques might 
be used to replace or assist the operator in tracing out 
individual planimetric features. A more fruitful area, 
as discussed in an accompanying paper* appears to be 
automatic scanning of the entire stereomodel in the 
profiling mode, gathering data which can be pro- 
cessed to directly generate color-separation manu- 
scripts. 
Expanding the Role of the Computer 
Even though the computer in the present auto- 
mated analytical stereoplotter performs major func- 
tions in plotting motion generation and overall con- 
trol, much of its potential for data storage, data 
processing, and decision making remains untapped. 
Examples of some of the more significant possibilities 
in this area are: 
12 
(1) Increasing the sophistication of the plotting 
control programs to handle more complicated 
situations, particularly those encountered in 
mountainous terrain. 
(2) Providing more extensive processing between 
basic model-coordinate data gathered in auto- 
matic plotting and the output information 
plotted on the coordinatograph. 
(3) Preprocessing the stereomodel to gather and 
store rough metric and image quality informa- 
tion which can provide guidance during the 
detailed plotting. 
One of the best illustrations of more sophisticated 
plotting control is the potential use of the computer 
to provide automatic fill-in of the small gaps in the 
plotted lines. In a typical situation the operation 
would be as follows. Contouring in mountainous ter- 
rain, the system plots accurately until a sharp ridge or 
valley is reached. Then, as the system negotiates the 
turn, a transient elevation error occurs, the stylus is 
raised, and a small gap is generated. Generally in these 
situations, the correlation system relocates the terrain 
surface without computer assistance, but occasionally 
the automatic search routine is employed to regain 
correlation. In either event, the point where auto- 
matic plotting is restarted is, by definition, a good 
point; therefore, a special gap fill-in program could be 
called on to plot in the reverse direction across the 
gap until a point close to the initial point is reached, 
and then return to the end of the gap and initiate 
plotting in the normal direction. If the'system be- 
comes lost during this operation, then it is not pos- 
sible to automatically plot across the gap (the system 
has attempted to do so from both directions and 
failed). However, experience indicates that this strate- 
gy would be highly successful in mountainous terrain. 
Temporary storage of the model-coordinate plot- 
ting data and automatic editing of this data before it 
is permanently plotted would provide an efficient 
means for improving the manuscript. This approach 
would allow questionable information just prior to a 
gap to be discarded. Contour data could also be 
smoothed to eliminate the effects of system noise or 
to provide a small amount of generalization of the 
terrain shape, if desired. At the same time, the plot- 
ting line could be adjusted to approximately compen- 
sate for the effects of finite scan size in curving ter- 
rain, and line gaps too small to require editing could 
be filled in. This type of process might be performed 
within the control computer by delaying the plotting 
TR. M. Centner and E. D. Hietanen, “Automatic Pattern Recogni- 
tion Techniques for Photographic Analysis." 
*ibid. 
CHAPELLE, WHITESIDE, AND BYBEE 
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