Lmh. Ulander, RADIOMETRIC SLOPE CORRECTION OF SYNTHETIC-APERTURE RADAR IMAGES, IEEE transactions on geoscience and remote sensing, 34(5), 1996, pp. 1115-1122
The brightness in a SAR image is affected by topographic height variat
ions due to 1) the projection between ground and image coordinates, an
d 2) variations in backscattering coefficient with the local scatterin
g geometry, This paper derives a new equation for 1), i.e., the radiom
etric slope correction, based on a calibration equation which is invar
iant under a coordinate transformation. An algorithm is described to o
btain the slope correction from a SAR interferogram, which also enable
s retrieval of the full scattering geometry, Since the SAR image and i
nterferogram are derived from the same data set, there is no need to m
atch the image with the calibration data, There is also no need for ph
ase unwrapping since the algorithm only uses the fringe frequencies, A
maximum-likelihood estimator for the fringe frequency is analyzed and
the algorithm is illustrated by processing ERS-1 SAR data, The exampl
e demonstrates that the spatial resolution and calibration error are a
dequate for most applications.