COMMISSION VII R2
Appendix to the.INT. ARCHIVES OF
PHOTOGRAMMETRY, Vol. XII:4, 1956
THE ROLE OF PHOTO-INTERPRETATION IN AIR FORCE CHARTING
by
Louis J. Reed, Cartographer
Aeronautical Chart & Information Center
U. S. Air Force
1. Photo-interpretation has been defined within the Air Force as the
science of extracting information from a photograph by identifying the
objects imaged on it and deducing their inter-related significance. It can be
said the science originated with the advent of the aerial photograph and has
grown along with photgrammetry with which it has always been closely
associated. Photo-interpretation gained recognition as a separate entity
several years ago when special techniques were developed to provide a more
practical solution for highly specialized needs; examples common in the
United States are forest studies, wildlife counts, geologic surveys, crop and
vegetation studies, military purposes, and many others. Today all photo-
grammetrists must be involved in photo-interpretation in various degrees.
The science of photo-interpretation has now become an important element in
the make-up of the Air Force cartographer; the cartographer cannot compile
today without using photographs to a major extent. So we come to agree,
generally, that all mappers and chartmakers are now embracing photo-inter-
pretation. Even those of us engaged in control extension by means of precise
stereoscopic plotting instruments must employ certain identification tech-
niques. No different are the personnel at the Aeronautcial Chart and
Information Center in St. Louis, Missouri, USA, where Air Force charting is
accomplished aided by the application of photo-interpretation techniques.
Some of the general requirements for aeronautical charts and charting
photography will be explained, and some of the special problems solved
through photo-interpretation will be discussed.
2. Aeronautical charts encompass a wide range of scales from 1:25,000
to 1:10,000,000. One of the latest to be introduced is a 1:2,000,000 jet naviga-
tion chart for high-speed aircraft, but the most well known is the World
Aeronautical Chart at 1:1,000,000 which has world coverage as the name
implies. Next larger in scale are the standard 1:500,000 and 1:250,000 charts
covering vast areas of military interest. Other principal chart series, which
may in some cases be mosaics, have scales of 1:100,000, 1:50,000 and 1:25,000,
but their coverage is limited to local areas. Finally, there exists a great
many special-purpose charts throughout the scale range. All have specific
uses; each one is designed to satisfy a particular need. Collectively, all these
charts represent our Air Force’s need today. Naturally the requirements
and specifications for each chart are somewhat different, and the cartog-
rapher must be capable and ready to adapt himself to any of them in his
application of photo-interpretation techniques.
3. Generally, the amount of detail and relative placement accuracy
required have been in direct proportion to scale, decreasing as scale decreases.
This has been true since, for example, detail has had to be sacrificed when
chart coverage was expanded. But this criteria is changing rapidly with the
coming of jet aircraft; already the tendency is toward even less detail than
the scale implies. However, position requirements do not decrease along
with detail when producing navigation charts for use by high-speed aircraft.
In brief, the time element has become a controlling factor in the design of jet
charts. Navigators have little time in flight to glance at their charts and
select features from it to identify as they pass over. But they must have a
few features for guiding purposes, and equally important, those few features
must be charted in correct relative position. The proper identification and
portrayal of such guiding features is an important part of our work.
4. A very real problem presents itself today when thinking of chart
