Applications of radar simulation 
Stereo viewability evaluation 
The digital elevation model of two Greek islands, Cephalonia .and. 
Ithaca, was chosen as the height model for stereo investigations. 
During the SIR-A flight (Nov. 1981) these islands were imaged at 
two different data takes on crossing swaths. The obtained stereo 
pair proved to be an alternative in its quality to same side 
stereo. 
The SIR-A radar parameters (Cimino and Elachi, 1982) were used as 
input parameters to the simulation, only modified in their stereo 
arrangements to obtain 
- Same side stereo / different elevation angles 
- Same side stereo with applied squint angle 
= crossing swaths stereo / same elevation angle 
A set of images was created for each of the investigations. The 
viewability was rated by  stereoscopic viewing using hard copy 
images and a standard stereoscope. 
Results: 
Elevation angles ranging from 15 deg. to 80 deg. were used for 
the same side investigations. A combination of 70 deg. vs. 50 
deg. elevation angle was found to be best for the Greek island 
elevation model and at flight altitude of 264 km (Fig. 1 and 
Fig. 2). The highest ranked stereo pairs are listed in Table 1. 
A variation of different squint angles (T = 0.5 deg. to 50 deg.) 
was applied to the best rated same side stereo image pair. 
When imaging in a cone but recording the backscatter in one line 
the output image is geometrically and radiometrically distorted. 
(Fig... 3). The locations of the image pixels need to be 
rearranged using simple equations (see Domik et al., 1983) in an 
additional step to the simulation to create the geometry of 
imaging in a plane perpendicular to the flight velocity vector 
(Fig. 4). The radiometric distortions, however, increase with 
the squint angle, and proved to be "not acceptable" by applying 
Squint angles of more than or equal to 30 deg. 
The Greek Island SIR-A picture imaging with two tracks crossing 
at an angle of 34 deg. created a good stereo pair. Simulation 
showed that there were no stereo viewability problems up to 40 
deg. of crossing angle. The viewability limit lays between 40 
deg. and 42 deg.