motors are attached to the projector orientation motions, the 
tracing table motion is controlled by a set of xy drives, and 
the tracing platen is replaced by a cathode ray tube which 
performs an automatic correlation of the two images received, 
The error signal generated by the correlator drives the machine 
in one of three operational modes: 
1. Relative orientation. When the tracing rable is 
brought to the conventional points for relative orientation, 
the x error signal drives the correlator in elevation; the y 
error signal drives the servo motor for the appropriate 
orientation motion. In this way relative orientation is reached 
rapidly and accurately. 
2. Contouring. The correlator is set at a fixed 
elevation. The error signals are then directed to the xy 
table drive motors, and the tracing table plots the contour 
line on the map sheet. A human operator is still required to 
override when ground cover, buildings, etc. confuse the 
correlator, but even with this limitation, contouring is ac- 
complished approximately five times faster than by the unaided 
operator. 
3. Profiling. The horizontal motion of the tracing table 
is constrained along a line of any azimuth. The error signal 
then moves the correlator in elevation and the tracing table 
along the selected azimuth. 
At the moment, the output of the instrument is entirely 
graphical. Hence, although the contouring ability would add 
materially to the highway design system, the profiles are not 
immediately applicable. But the combination of the Stereomat 
and the next instrument to be described would fit the bill 
exactly. 
The Integrated Mapping System is under development by 
Fairchild Camera and Instrument Corporation for the Army Map 
Service, There are three instrumental components to this 
system. 
1. A modified double projection stereoplotter. The 
heart of this system is shown in Figure 7. The tracing table 
is motor driven in the x direction along a bar which can be 
moved in selected small increments of y. The essential 
operation of the plotter is thus to trace out successive 
profiles. On the first pass the elevation of the tracing 
platen is controlled by the operator. At the same time the 
elevation versus x position are recorded digitally on magnetic 
tape. This tape can then be used to drive the platen back 
across the same profile so that the operator can monitor what 
he has done and override it where it seems necessary. When 
he is satisfied with the profile he can commit it to memory 
13