is several times faster than most of the medium-scale computers 
which are currently in use. As an example of the speed of the AP-C 
computer, consider the standard analytical stereoplotter programs. 
Within a time interval of about 38 milliseconds, the computer starts 
with the coordinates of a given point in the stereo model, adds cor 
rections for earth curvature and atmospheric refraction, translates 
the model coordinates to the perspective center of each photograph, 
rotates each set of coordinates about the three orientation angles, 
converts these coordinates to photo scale, applies corrections for 
lens distortion and film shrinkage, and supplies commands to the 
servo mechanisms to properly position the photographs. 
The remainder of this paper describes operations which the 
AP-C system either has been or can be programmed to perform. 
These have been categorized as using either the standard AP-C 
programs, modified AP-C programs, or new programs. 
STANDARD AP-C PROGRAMS 
In addition to the programs which are supplied to permit oper 
ation of the AP-C system as an analytical stereoplotter, there are a 
number of programs provided with the system which can be used for 
other purposes. These are (1) a straight-line distance routine, (2) a 
punch-coordinates routine, and (3) an X-Y plotter program. 
The straight-line distance routine is intended as an aid in 
scaling a stereo model. It measures the distance between any two 
points in the model that the operator designates. Obviously, this 
routine can be used to measure the length of any straight line in the 
stereo model, such as the side of a field or the length of a straight 
road. The routine can also be used to find the point which is any 
arbitrary distance from a reference point. A possible example is 
reading the coordinates of a highway route at predetermined intervals. 
The punch-coordinates routine causes an identification number 
and the current X, Y and E coordinates of the reference mark in the 
stereo model to be punched out on paper tape. If desired, the coordi 
nates may also be typed at the same time. The output of this routine 
may be kept as a permanent record or used for further data-processing 
operations.