Automation in 
Photogrammetric Compilation 
W. E. CHAPELLE An automatic system which can fully replace the operator of a photogrammetric 
A. E. WHITESIDE compilation instrument has not yet been developed, a fact which is perhaps not 
JE BYBEE surprising in view of the wide range of mechanical and intellectual skills required in 
manual compilation. However, systems which automate the more routine operator 
tasks of stereoperception and plotting have been successfully applied to a number of 
instruments. This paper discusses the use of electronic scanning and correlation tech- 
niques for the basic terrain-sensing function required in automatic stereoperception. It 
also shows how the information sensed by the correlation equipment can be used by 
the stored-program digital computer of an analytical stereoplotter to automatically 
plot contour and profile manuscripts. The final sections discuss potential approaches 
for improving the automatic stereoperception equipment and expanding the role of 
the computer to improve system performance and further increase the degree of 
automation. 
INTRODUCTION 
In most stereocompilation instruments, a human 
operator is an integral part of the operational process. 
In analytical instruments, such as the AS-11A and 
AP-C stereoplotters, the operator's task has been 
simplified in various ways, for example, by automat- 
ing the computational aspects of stereomodel setup 
and output scaling. In these instruments, however, as 
in the simplest projection-principle plotters, all on- 
line measurement and control functions are per- 
formed by the operator. 
The universal requirement for increased produc- 
tivity in stereocompilation has prompted develop- 
ment of automatic equipment to provide greater 
compilation speed and to eliminate quality-control 
problems associated with operator fatigue. The de- 
velopment of effective automatic equipment has 
proved to be a formidable task, primarily because of 
the highly complex and diversified nature of the func- 
tions performed by the instrument operator. 
For subsequent discussion, it is useful to separate 
the operator's functions into four general areas: 
(1) Stereoperception and Measurement 
The operator views the optical model 
created by the instrument and manually ad- 
The discussion of automation techniques presented in this paper is 
based primarily on the automated analytical stereoplotters developed 
by Bendix Research Laboratories under the sponsorship of Rome Air 
Development Center, U. S. Air Force. 
BENDIX TECHNICAL JOURNAL SUMMER 1968 
justs a reference mark to establish or maintain 
contact with the apparent terrain surface. This 
process is basic to all stereomensuration in- 
struments. 
(2) Plotting Motion Generation 
In manual compilation, the operator intro- 
duces the model-coordinate motions required 
to trace out lines of interest, simultaneously, 
of course, maintaining the reference mark in 
contact with the terrain surface. 
(3) Photointerpretation 
In many situations, the operator must ex- 
amine the imagery to recognize certain terrain 
features in addition to measuring or plotting 
their positions. As examples, the operator per- 
forms photointerpretation functions in tracing 
out planimetric features and in compensating 
hypsographic plots for the heights of trees and 
other obstacles. 
(4) Overall Control 
In the typical stereocompilation process, 
the operator must make a series of operator 
decisions and judgments concerning planning, 
sequencing of operations, and editing. 
Thus, manual operation of a stereocompilation instru- 
ment requires application of a wide range of human 
skills, both mechanical and intellectual. It can be ex- 
pected, then, that an automatic system which re-