"Paul Hirose" wrote

When a Doppler ground mapping technique is being employed the
direction of your line of sight matters a lot. The difference in
Doppler between targets A and B is very small. On the other hand, C
and D are in the position of max Doppler difference and are much
easier for the radar to resolve. The size of this difference is not
the only factor involved, but it's very important.

-- A
B



C D

Targets C and D are known as "tangential targets." That is, their Doppler
is getting close to zero. The benefit of SAR is not really in the Doppler. It
is in the long look at the target. Targets straight ahead would be like looking
off the side of your parabolic antenna. What you want is a parabolic
antenna that is 5 miles wide:

---------

C D

Now you can crunch the target data and simulate say an effective 1 degree
beam with a physical 3 degree beam (which at 5 miles can cover a whole
city block, while a 1 degree beam can focus on buildings).