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SATELLITE SYSTEMS FOR CARTOGRAPHY 
Frederick J. Doyle 
U. S. Geological Survey 
Reston, VA 22092, USA 
ABSTRACT 
Mapping from remote sensing records requires image information content 
and geographic referencing accuracy which are related to the scale of 
the published map. However the extraction of cultural planimetric de 
tail requires a ground resolution of about 3m/£p or 1.5m/pixel regard 
less of the scale of the final map. The requirements for 1:50,000- 
scale mapping are not met by Landsat-4 or the SPOT system. The Metric 
Camera experiment on Spacelab-1 and the Large Format Camera currently 
planned for Shuttle Missions STS-11 and STS-17 will both provide re 
covered film data suitable for mapping at 1:50,000 scale. An electro- 
optical system called MAPSAT has been proposed by the U. S. Geological 
Survey to meet the same requirements. 
INTRODUCTION 
From the earliest days of the space program cartographers have expected 
that photography from space vehicles would result in the same increment 
of productivity which came about when aerial photography replaced ground 
surveys. Photographs from the early manned missions, Mercury, Gemini, 
and Apollo provided spectacular views of the Earth, and experiments 
showed that it would be possible to assemble image maps at scales of 
1:250,000 or smaller, but that the resolution would be inadequate for 
compiling roads, railroads, urban areas, and other cultural features 
which one normally expects to find on maps, regardless of their scale. 
Partly as a consequence of this deficiency, partly for fear of politi 
cal implications of high resolution photography, but mostly in response 
to a perceived need for classifying land use, geologic structures, and 
agricultural productivity on a countrywide basis, the Landsat systems 
were not designed for topographic mapping. It is the purpose of this 
paper to address the problem of topographic mapping from space. 
RESOLUTION REQUIRED FOR MAPPING 
The fundamental content of a photogrammetric map is provided by ground 
resolution of the images, expressed in meters per line pair for photo 
graphic systems, or in meters per pixel for electro-optical systems. 
There is a direct relationship between ground resolution and the useful 
scale at which images can be reproduced. (Doyle, 1973) 
The resolving power of the normal human eye at usual reading distance of 
25 cm is about 7 line pairs per millimeter (£p/mm). Thus the smallest 
dimension which can be observed in the image is 1/7 mm, and for photo 
graphic systems the relationship between ground resolution R m (in m/£p) 
and image scale number S m is given by 
^m 
which may be rewritten 
1 mm 1 m e 
7 £p 1000 mm m 
S m = 7000 x R m 
(1)