Incompatible and incorrect situations are sensed 
and indicated to the operator. These include abnor- 
mal automatic plotting situations and incorrect 
photogrammetric parameters. In the automatic spot 
height measurement mode of operation, the existence 
of a low correlation quality (indicative of inability to 
maintain proper image alignment) is detected and 
used to alert the operator. 
ORTHOPHOTO ATTACHMENT 
An electronic orthophoto printer attachment being 
developed for the AS-11B-1 system is based upon the 
electronic orthophoto attachment previously con- 
structed for the AS-11B/C experimental automated 
analytical stereoplotter system. The attachment has 
the capability of being simultaneously connected to 
three stereoplotter systems. It works on a time-shared 
basis but operates from only one stereoplotter at a 
time. Since the orthophoto attachment is presently 
being designed, its details will not be discussed here. 
EXPANSION POSSIBILITIES 
The AS-11B-1 computer magnetic core memory 
can be readily expanded from 8,192 words up to 
32,768 words. Expansion to 16,384 words can be 
achieved directly; for expansion to 32,768 words, a 
small amount of new hardware is needed. The ex- 
panded memory can be used to permit programs for 
all system modes and functions to be stored in 
memory at all times. Additional memory can also be 
used for the necessary programs and data to perform 
the expanded functions discussed in subsequent 
paragraphs. 
A typewriter unit can be readily attached to the 
AS-11B-1 computer. Capabilities for the attachment 
of a Teletype typewriter unit have been designed into 
the computer, although a typewriter is not currently 
provided in the system. Provision of the typewriter 
permits direct output in hard copy form of system 
data, from point coordinates to photograph orienta- 
tion information. 
A magnetic tape recording and reading unit can be 
attached to the computer. Basic provisions for the 
attachment of such a tape unit have been made in the 
AS-11B-1 computer design. A magnetic tape record- 
ing unit can be used for recording plotting data in 
digital form for direct entry into a digital carto- 
graphic data system. Magnetic tape reading and re- 
cording can also be used for program data and for 
stereo model data. 
The computer can be connected to a remote large- 
84 
scale computer. This can be accomplished in a num- 
ber of ways to provide different levels of data transfer 
capability. Such a connection to another computer 
might be used for the direct transfer of cartographic 
data, for the entry of control and correction data into 
the analytical stereoplotter system, or for the storage 
and retrieval of general stereoplotter operation in- 
formation. 
The operating computer programs can be ex- 
panded to accommodate other types of photography 
or corrections for other types of photographic non- 
idealities. An example of the former is strip photog- 
raphy. An expanded capability for correcting non- 
idealities can be provided by writing programs that 
compensate for complex photograph distortions on 
the basis of reseau measurements. 
Programs to perform off-line computations related 
to stereocompilation can be prepared, for example, a 
program to compute polynomial coefficients for the 
model deformation corrections. Such a program 
would accept the correct ground coordinates of con- 
trol points and the current model coordinates of the 
same points and would compute the coefficients of 
correction polynomials to compensate for the model 
deformations according to the method of least 
squares. Off-line programs can also be developed for 
the computation of correction parameters for other 
corrections made by the system. 
The AS-11B-1 system is capable of being inter- 
faced with several types of orthophoto attachments, 
including an optical orthoprinter, for either on-line or 
off-line application. These possibilities, when prop- 
erly implemented, may produce significant advances 
in orthophotography. Orthophoto generation is dis- 
cussed in more detail in an accompanying paper* and 
in Reference 2. 
CONCLUSION 
The AS-11B-1 is a new automatic stereoplotter 
that reaches toward the future in its design and imple- 
mentation. It is solidly based on the experience and 
knowledge accumulated from the design, building, 
and use of its predecessors. The AS-11B-1 expands 
from this basis toward higher performance, wider 
versatility, and in particular, toward more sophisti- 
cated and comprehensive photogrammetric-carto- 
graphic processing systems. 
REFERENCES 
1. Gino Parenti, “Analysis of the Mechanical-Optical Design of the 
Analytical plotter,” Canadian Surveyor (June 1963) pp. 148-154. 
2. U. V. Helava, “On Different Methods of Orthophotography,” 
Canadian Surveyor (March 1968) pp. 5-20. 
HELAVA, WHITESIDE, AND MATHERLY 
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