The effect of topography on SAR calibration

During normal synthetic aperture radar (SAR) processing, a flat Earth is assumed when performing radiometric corrections such as antenna pattern and scattering area removal. The authors examine the effects of topographic variations on these corrections. Local slopes will cause the actual scattering area to be different from that calculated using the flat Earth assumption. It is shown that this effect may easily cause calibration errors larger than a decibel. Ignoring the topography during antenna pattern removal may also introduce errors of several decibels in the case of airborne systems. The effect of topography on antenna pattern removal is expected to be negligible for spaceborne SARs. The authors show how these effects can be taken into account if a digital elevation model is available for the imaged area. The errors are quantified for two different types of terrain, a moderate relief area near Tombstone, AZ, and a high relief area near Oetztal in the Austrian Alps. The authors show errors for two well-known radar systems, the C-band ERS-1 spaceborne radar system and the three frequency NASA/JPL airborne SAR system (AIRSAR). >

[1]  J. Zyl,et al.  Calibration of polarimetric radar images using only image parameters and trihedral corner reflector responses , 1990 .

[2]  Valdis V. Liepa,et al.  A general polarimetric radar calibration technique , 1991 .

[3]  R. Goldstein,et al.  Topographic mapping from interferometric synthetic aperture radar observations , 1986 .

[4]  Anthony Freeman,et al.  Radiometric correction and calibration of SAR images , 1989 .

[5]  F. Bonn,et al.  Radiometric correction of C-band imagery for topographic effects in regions of moderate relief , 1988 .

[6]  E. S. Kasischke,et al.  Phase calibration of polarimetric radar images , 1989 .

[7]  T. Bayer,et al.  Correction of relief effects in sar-images of vegetated areas , 1990, 10th Annual International Symposium on Geoscience and Remote Sensing.

[8]  Anthony Freeman.  A new system model for radar polarimeters , 1991, IEEE Trans. Geosci. Remote. Sens..

[9]  Jakob J. van Zyl,et al.  Calibrated imaging radar polarimetry: technique, examples, and applications , 1991, IEEE Trans. Geosci. Remote. Sens..

[10]  C. Werner,et al.  Polarimetric SAR calibration experiment using active radar calibrators , 1990 .

[11]  Howard A. Zebker,et al.  Phase calibration of imaging radar polarimeter Stokes matrices , 1990 .

[12]  J. Zyl.  A Technique To Calibrate Polarimetric Radar Images Using Only Image Parameters And Trihedral Corner Reflectors , 1989 .

[13]  R. Wildey,et al.  Radarclinometry for the Venus radar mapper , 1986 .

[14]  M. A. Tassoudji,et al.  Calibration of polarimetric radar systems with good polarization isolation , 1990 .

[15]  P. W. Vachon,et al.  Synthetic aperture radar calibration using reference reflectors , 1990 .

[16]  J. D. Klein,et al.  Quadpolarization SAR calibration using target reciprocity , 1991 .