PHOTOGRAMMETRIC ENGINEERING 
iyi | N 
fl 
| MN 
  
  
Fic. 1. Contour Plot from profile scanning. 
uses to which they may be put. In the Inte- 
grated Mapping System, the orthophoto- 
graphs would be produced automatically as a 
product of the single profile scanning opera- 
tion, and they would provide the basic source 
material for planimetric compilation. 
The feasibility of using orthophotographs 
in this manner has been tested to a limited 
extent. A pair of orthophotographs was sup- 
plied to a compiler who produced color- 
separated drawings by scribing on translucent 
material placed directly over the orthophoto- 
graphs on a light-table. Where he found 
stereoscopic examination desirable, he worked 
with a stereoscope, using a print of the origi- 
nal photography and an orthophotograph as a 
stereopair. He found this method of working 
quite convenient. The color-separated ma- 
terial produced in this manner was compared 
with that produced from a manuscript based 
on the original photography and compiled 
conventionally in a stereoplotting instrument. 
2 
'The positional accuracy and completeness of 
the detail produced by the two methods were 
found to be substantially equal. 
The dashed-line contour plot and the ortho- 
photograph which are produced by profile 
scanning provide sufficient information for 
map compilation. Nevertheless, a third type 
of data is extracted from the stereoscopic 
model and retained. This is a continuous 
record, on magnetic tape, of all profiles. The 
tape records Z as a function of X for very 
small increments of X along a profile. (In the 
equipment being built, X is the direction of 
scan, with successive profiles displaced in 
regular increments of Y.) This record, which 
contains much more complete relief informa- 
tion than the contour plot, is useful in several 
ways. It is used internally to aid the profile 
scanning operation, as will be explained in a 
later section. It can also be used to activate 
and guide an automatic milling machine for 
the purpose of carving master terrain models. 
Such a machine is now being built for this 
purpose. 
These, then, are the general features of the 
system. It is evident enough that maps can be 
made in this way. The question that naturally 
arises is what we hope to gain by thus scram- 
bling the mapping process. The main poten- 
tial advantages of the system are: 
a. Reduction in stereoplotting time required 
for each stereo model. As long as the time re- 
quired for profile scanning is less than the 
sum of the times required at present for con- 
touring and for the compilation of planimetry, 
the output of maps could be increased, where 
timeliness is important, without additional 
stereoplotting equipment or trained opera- 
tors. It should be noted that the foregoing 
statement does not necessarily mean that 
overall efficiency would be increased. It sim- 
ply means that a number of people not 
trained in stereoplotting would be able to get 
to work on a given model at an earlier stage. 
An actual reduction in the number of man- 
hours required for a map would require that 
the profiling time be comparable to the time 
necessary for conventional contouring. 
b. Savings in elapsed time through combina- 
tion of compilation and color separation opera- 
Hons. This saving is made possible by the use 
of the orthophotograph as a guide for color- 
separated compilation. 
c. Substantial improvement in the efficiency 
of terrain model construction. The use of stored 
profiles to guide an automatic milling machine 
would result in the production of a master 
terrain model with virtually no expenditure of