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limitations for multispectral displays and for equivalent 4 
digital processing techniques [41], [42]. 
5 2 of the ERTS imagery is expected to be precision processed, 
This will involve differential correction of the bulk images 
by interpolation to ground control according to: 
Ax = a E * uud * a, x + a 
2 
2 
= X. ° 
Ay = b, E «qd J pon Sp EVE y (15b) 
In order to determine the correction coefficients valid been 
4 control points an automatic comparator with image correla- 
tion between control images prepared for the control points 
and between the bulk imagery is being designed by Bendix. 
The corrections derived can be used in a new electron beam » 
recording at a UTM projection at a scale of | : 1 000 000 on 
230 x 230 mm film. The geometrical accuracy of these images 
and their registration by this procedure is expected to be 
between 55 and 85 m. 
IBM has developed computer programs for correcting bulk and 
precision images by the electron beam recorder [43]. 
While producing the precision images the opportunity is also 
provided for image digitization. Further evaluation may 
therefore be carried out by complete digital processing. 
  
The ERTS development is of special significance to remote 
sensing in general. It initiates costly developments in 
hybrid display and digital processing techniques, which may 
become of general use in remote sensing, and which are a 
prerequisite for objective spectral and temporal ananog or e" 
digital image comparison techniques, which have sofar in 
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ex]