A radar system derives a correction for an actual boresight (311) of a
radar monopulse antenna mounted on a moving platform from .SIGMA. data and
.DELTA. data generated with respect to an a priori known, calibrated
boresight (309). The monopulse antenna (602) is coupled to a ground
position measuring system (616) while acquiring data. The radar receiver
acquires a .SIGMA. and .DELTA. synthetic aperture map of the same radar
scattering location with respect to the calibrated boresight. .SIGMA. SAR
data and the .DELTA. SAR data are motion compensated using the position
and velocity supplied by the ground positioning system. A computer forms a
ratio of the aligned .DELTA. pixels to the aligned .SIGMA. pixels for each
of a plurality of aligned .SIGMA. pixels located near the calibrated
boresight. The correction for the location of the actual boresight of the
monopulse antenna is computed by an analysis of the ratio of aligned
.SIGMA. pixels and corresponding aligned .DELTA. pixels over the radar
scattering location. Typically, a least square fit analysis is used to
plot the .DELTA./.SIGMA. ratio, and ascertain where the zero crossing of
the monopulse angle=0 line is found thereby identifying the position of
the actual boresight, and the correction from the a priori, calibrated
boresight.
