24. 
smaller and lighter movable scanning element and shorter travelling ranges, will 
result in a probably vast improvement in the already excellent performance of 
the device. This is an important recognition since there is no necessity to 
speculate on any further basic improvements of the automatic stereo device 
itself to improve its present performance. 
The accuracy of automatic stereoplotting operations is very high and 
in some instances seems to be even better than that of a human operator. In 
particular, its amazing accuracy in removing the vertical parallax (relative 
orientation) suggests some interesting applications of the device. 
The repeatability and the accuracy of determination of spot elevations 
is remarkable. An allowance must be made for the coverage of the terrain. The 
device in the presentform cannot interpret the contents of the photographic image 
and therefore cannot differentiate between the actual ground surface and the 
coverage. However, lessening the influence of scattered objects (trees or houses) 
on height determinations seems to be realizable. 
When compared with contouring by a human operator automatic con- 
touring is extremely rapid. The lowest present speed of automatic contouring, 
including the operator time necessary for possible corrections and checking of the 
completeness of the plot, is two to four times faster than conventional contouring 
by a human operator. But speeds of up to ten to fifteen times faster are already 
attainable at present withonly a relatively smalldrop in accuracy. Contouring by 
the automatic stereoplottingdevice requires the supervision of a human operator, 
but the extraordinary gain in speed of operation would more than justify froma 
purely economic point of view the use of the device. 
The accuracyof automatic contouring is not quite as highas the accuracy 
of conventional contouring performed on the same type of plotter. The difference 
is not great and a certain drop in accuracy could be compensated for by the use 
of larger-scale photography, but still with a substantial economic gain because of 
the high speed of the automatic operation. 
A problem which requires some modification in the present device is 
the contouring of very flat areas. This would probably have no great effect on 
the contouring accuracy but would considerably smooth the automatic contouring 
process and reduce further the necessity for interference by a human operator. 
There are evident ways of solving this particular problem. 
The present device cannot plot planimetric details automatically. How- 
ever, since it can keep the floating mark continuously on the surface of the stereo- 
model it could lead to a significant increase in the speed of planimetric plotting. 
This however would again require its adaptataion to a non-anaglyphic plotter, 
because this would permit the separation of the ordinary floating mark from the 
scanning pattern. This solution, when combined with the use of a steering device, 
could have further economic significance of the automatic mapping. 
Finally, there is nodoubt that complete automation and the mathemati- 
cally correct treatment of redundant observations on the plotter can be achieved 
only by combining the automatic stereoplotting device with an analytical plotter, 
which will offer many advantages that do not exist in conventional plotters.