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.