struction of new devices are made by Leberl in [36]. The 
rectified images will still show image displacements due 
to topography. Such displacements may then be eliminated, 
if considered necessary, by evaluating the rectified stereo- 
images on an orthoprinter. 
For satellite imagery special conditions exist. Earth satel- 
lites produce imagery from such high .erbits, that irregulor 
topographic displacements, which need to be corrected by 
human or automatic image correlation, do not appear. The 
rectification merely becomes a task to find a suitable map 
projection for the imaged sphere. of. the earth. 
The first application of analytical techniques to geometric 
processing of satellite imagery was introduced for the 
Nimbus project [3714 [38i ; [39]; while Nimbus images were 
not rectified the geometric problem was substituted by 
superpositioning a computed latitude - longitude grid by 
tick marks on the imagery. 
The Earth Resources Technology Satellite program [12]. pro- 
vides concentrated impetus to solve the geometric problem by 
differentially rectifying the images [ 40]. Both types of 
ERTS images (the 3 camera Return Beam Vidicon Television 
imagery (RBV) and the four channel Multispectral Scanner 
imagery (MSS)) will be printed by a hybrid system, designed 
  
by CBS, an analog electron beam recorder, which is controlled 
in position and intensity by a digital computer. All images 
will be differtially rectified according to tracking, atti- 
tude, projection and calibration data to obtain bulk images 
on 70 mm film at the scale 1 : 3,370,000 using a UTM-pro- 
jection. Absolute errors for these bulk images are expected 
to be in the magnitude of * 900 m on the eround. The three 
RBV images are expected to register within 300 m and the 
four MSS images within 100 m. These estimates constitute 
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