With reference to the type of the initial coordinates, 
in the first case the transformation is accomplished by a 
so-called "object space algorithm", in the second by an 
"image space algorithm". 
2.1 Map-to-Image Registration 
By applying the object space algorithm, cartographie 
information can be displayed in an original SAR image. A 
three-dimensional digital map, which may be taken as a 
digital landscape model, is created. by bringing a digital 
terrain model (DTM) into a defined cartographic projection, 
using two-dimensional data (linear and aereal features) 
derived from topographic and/or thematic maps. The above 
transformation is then used Lo. obtain ‚registered. map 
overlays (Lukes and Raggam 1986), which could then easily be 
retransformed into the object space. 
Map-to-image registration plays a role in all 
applications, which are sensible to grey value changes due 
to geometric corrections, e. ge geocoding, and where 
therefore the experts favourably want to. evaluate the 
unchanged SAR imagery. Potential fields of employment of 
this procedure are the general task of map-guided data 
acquisition from. SAR .image. and, in. particular, earth 
resources exploitation requiring frequent monitoring. 
It certainly is a deserving task to extend this idea to 
three-dimensional thematic data that can be compiled from 
any type of stereoscopic remote sensing data, e. g. using 
an. analytical plotter, though without in the first instance 
having the data linked to a defined cartographic projection. 
SAR Image Simulation 
Another important utilization of the radargrammetric 
model lies. in. the possibility. to .transform the digital 
landscape model as a whole or in parts into the image space, 
thereby creating a synthesized SAR-like image. In order to 
obtain an image displaying realisitic grey values, a 
radiometric model capable to incorporate backscatter 
variations due to different surface types and speckle noise 
appearance is needed. The process comprising these elements 
is known as SAR image simulation. 
Due to the complexity of radar physics, the radiometric 
models are still far from providing a sound basis for true 
image intensity simulation. In a number of investigations, 
the reconstruction of the mapping geometry is indeed the 
ma jor aspect, whereas the correct representation of surface 
signature and speckle is less significant. On the other 
hand, simulation can be a useful tool: .to. . analyze the 
radiometric properties of a real SAR image: 
324