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Title
The role of digital components in photogrammetric instrumentations

CARTOGRAPHIC UTILITY OF SPACE PHOTOGRAPHS
Frederick J. Doyle
In October 1971, an International Symposium on Orthophotomapping was
held in Paris, France. At that time the theoretical basis for preparing
orthophotomaps from space photography was presented (1)*. Also presented
were the characteristics of the imaging systems to be carried on the Earth
Resources Technology Satellite (ERTS-1) and the Skylab. This was followed
by a projection of the cartographic applications which could be accomplished
from these records.
The ERTS-1 spacecraft was launched in July 1972 and has been oper
ating continuously since that time. The three manned occupations of
Skylab have been completed, and all data have been obtained. Though it
is still too early to reach final conclusions on the value of these
records, it is appropriate to review what has been accomplished and what
has been learned about the utility of these types of space photographs
for cartographic applications.
Theoretical Basis
The major advantages of space photography for preparation of ortho
phot omaps are:
1. Narrow angular field. This reduces image displacements
due to topographic relief and makes possible the production
of orthophoto products without the necessity of differential
rectification.
2. High image resolution. This is made possible by the
combination of narrow-field optical systems and extremely
stable vibration-free platforms.
3. Synoptic view. The ultra-high altitude of space vehicles
makes possible a wide area of coverage per frame despite the
narrow angular field.
Counteracting these advantages are:
1. Small image scale. Despite relatively long focal lengths,
the extreme altitude produces small-scale images.
♦Numbers in parentheses denote references.