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other alphanumerical. The former, which has nine 
decimal places, is used to display numerical quanti- 
ties, such as coordinates and parameters. The latter 
indicates which parameter or quantity is being dis- 
played. Values are entered from the control panel in a 
serial manner by using a set of pushbutton switches, 
labeled O through 9. 
In the AS-11B-1 system, an operational control 
panel at the coordinatograph permits the operator to 
control and assist in automatic plotting while moni- 
toring the operation at the coordinatograph. This 
control panel is very practical; it is seldom necessary 
for the operator to go back to the viewer unit for 
monitoring or fill-in purposes. 
CORRELATOR 
The correlator of the AS-11B-1 has been incor- 
porated into the same cabinet with the computer. 
Thus, the entire electronic hardware is in one com- 
pact and well-integrated unit. This unit is truly the 
nerve center of the automatic operation. It controls 
the electronic image scanners; processes the signals 
from the scanners to obtain x and y parallaxes, ter- 
rain slope estimates, and predictive information; and 
performs all geometric computations, applies correc- 
tions, makes decisions on plotting strategies, and 
drives the servo systems to obtain the required re- 
sults. The functional features of the correlator and its 
relation to the CRT scanning system and the com- 
puter, as well as the interactions between the three 
and the automation programs, are of great impor- 
tance and interest, but it is not possible to discuss 
them in detail here.* It is important to note that 
advantages are obtainable by integration of all these 
important elements into one unified system. The 
AS-11B-1 represents an important step toward a func- 
tionally optimized system. 
PROGRAM FEATURES 
The new, powerful computer of the AS-11B-1 
makes it possible to design and implement more ef- 
fective and comprehensive programs. For example, 
the photograph coordinates are computed 200 times 
per second and with increased accuracy. With respect 
to improvement in accuracy, not only is numerical 
performance improved, but a better mathematical 
model can be achieved that includes a provision for 
arbitrary function corrections of the photocoordi- 
nates and an extra mathematical rotation in x. The 
former is a powerful tool for handling photo errors 
and unconventional photographs. The latter is useful 
for mathematical alignment of the imagery, for ex- 
NEW STEREOPLOTTER 
ample, to reconstitute a stereomodel on the basis of 
existing numerical orientation data. Additional flexi- 
bility is gained in that the programs are designed to 
handle wide ranges of parameters. For example, focal 
lengths can be virtually unlimited, and different for 
each of the two photographs. One set of programs 
handles a variety of camera geometries. 
Programs for relative and absolute orientations 
rival in sophistication and mathematical rigor many 
of the programs used in off-line analytical triangula- 
tion. A feature of special interest is the method of 
parameter perturbation discussed in an accompanying 
paper.* This is an example of a rather resourceful 
way of utilizing the requirements of real-time opera- 
tion to an advantage in a "conventional" problem. 
The orientation programs of the AS-11B-1 can derive 
either relative or absolute orientation or both, using 
large redundancy. At the end of the computations, 
the rms value of the vector residuals in photocoordi- 
nates is displayed. Individual point residuals are also 
available and may be displayed at the operator's 
command for checking purposes if the rms error is 
exceptionally large. Control data is accepted in any 
rectangular ground coordinate system; output data is 
displayed and recorded in the same coordinate 
system. 
The computer programs play an extremely im- 
portant role in the performance of the automation 
functions. The automation programs of the AS-11B-1 
include the basic features of efficient automation as 
implemented in present-day automatic photogram- 
metric systems. In addition, the automation programs 
reflect appreciation of practical operational effici- 
ency. Special attention has been paid to programs 
that help the operator’s supervisory tasks. The pro- 
grams perform automatic plotting acceleration and 
deceleration limiting, correct for limited correlator 
response, and employ delayed plotting, all to reduce 
plotting of incorrect data. Also, programs are in- 
cluded to avoid plotting when the reliability of the 
data is in question, to record the gap areas, and to 
return to the gap areas at operator’s request for auto- 
matic or operator-assisted fill-in. The automation 
programs also have sophisticated capabilities for re- 
covering a contour or profile line lost on account of 
ambiguity or questionable data. The searching pro- 
grams apply, in a rapid succession, different strategies 
to recover the line including trials with nonzero 
slopes. One or another strategy is usually successful 
without causing major loss in plotting time. 
  
*W. E. Chappelle et al, ‘“‘Automation in Photogrammetric Compila- 
tion.” 
*R. B. Forrest et al, “Programming Computer-Controlled Photo- 
grammetric Instruments.” 
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