In the standard AP-C system, the computer controls the oper 
ation of the coordinatograph by means of servo drives on the X and Y 
axes. It was a natural extension, therefore, to provide a program for 
operating the computer and coordinatograph together as a tape- 
controlled X-Y plotter. The stereo viewer and the programs for its 
operation are not used in the X-Y plotter mode of operation. 
For use as an X-Y plotter, the system requires an input data 
tape containing successive sets of X and Y coordinates. This can be 
the output tape from the punch-coordinates routine or a tape from 
some other source. The computer program reads one set of coordi 
nates from the tape at a time, rotates the coordinate system by any 
constant angle, scales each coordinate value by a separate scale 
factor, and commands the coordinatograph to trace a straight line 
from the last point to the current point. In order to maximize the 
speed of operation, the computer reads the coordinates of the next 
point from the input tape at the same time that a line is being traced 
to the current point. Tape reading time is about one second per point, 
so data can be plotted at a maximum speed of about 60 points per 
minute. 
POSSIBLE EXTENSIONS OF STANDARD PROGRAMS 
Several routines of the same general nature as the straight-line 
distance routine could be quite useful in applications such as the 
planning of highways or housing developments. These routines would 
measure distances or areas as described below. 
The first of these routines could be referred to as a path length 
routine. It measures the length of whatever path the instrument operato 
follows to traverse from one point to any arbitrary second point. The 
traversed distance is continuously displayed on the operator's control 
panel. Figure 3a illustrates the measurement which is calculated by thi 
routine. 
Two different types of area-measuring routines might also be 
programmed. One of these would be based on the assumption that the 
area has any number of straight sides. The operator would locate the 
reference mark at each corner of the enclosed area, pushing a button 
to signify to the computer that a corner has been located. After lo 
cating all corners, a second button would be pushed to command the 
computer to calculate the area. The result would be displayed at the 
operator's control panel and could also be typed or punched on tape.