International Archives of Photogrammetry and Remote Sensing, Vol. 32, Part 7-4-3 W6, Valladolid, Spain, 3-4 June, 1999 
Image coregistration may be facilitated, if the image data to be 
registered show reduced distortions already in their original 
form. This is achieved by small off-nadir incidence angles for 
optical data, whereas for SAR systems the off-nadir incidence 
angles should be large. A more detailed list of requirements to 
be met in order to simplify geometric pre-processing of remote 
sensing image data can be found in Schardt et al. (1999). 
New methods to geometrically register image data are still in 
development and will become operationally available. As one 
alternative, image coregistration on the basis of automatic image 
matching techniques has to be mentioned. It can be 
implemented as a to a large extent automated, end-to-end 
procedure for image geocoding. For sufficiently similar input 
images, satisfactory results have already been achieved with this 
procedure as implemented at the Institute of Digital Image 
Processing. For more complex situations, however, particularly 
for dissimilar images and for SAR imagery, the algorithms still 
need to be seriously extended and optimised to be applicable for 
operational image coregistration. 
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