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5 SUMMARY AND CONCLUSION 
The effects on DEM quality of estimating baseline using different methods are discussed. Baseline estimates using 
orbital information, provided in the leader file of the data, give a DEM with a residual slope. Also, the datum of the 
resulting DEM, in this case study, is well below the datum (mean sea level) of the reference DEM. Baseline estimate 
using image offset parameters also shows a similar trend but with a tilt in a different direction. If the fringe rate method 
is used alone produces discontinuities in the DEM because of poor estimation of the parallel component of the baseline. 
When combined with orbital parameters or image offset parameters to estimate the parallel baseline component, the 
fringe rate method provided comparatively better results, provided the fringe rate estimation window is placed over flat 
terrain only. Iterative methods of locating the best window location and best window size would reduce the tilt in the 
final InSAR DEM. 
ACKNOWLEDGEMENTS 
The author is grateful to her supervisor Prof. Paul M. Mather, University of Nottingham, for his guidance. The author 
also expresses her gratitude to NASA JPL for providing the SIR-C data, and to Prof. P.S. Roy and Mr. P.L.N. Raju, 
IIRS, Dehradun, India, for providing the Survey of India topographic map and IRS-1D PAN data for this study. The 
study is supported by a Commonwealth Scholarship. Computing facilities were made available by the School of 
Geography, University of Nottingham. 
REFERENCES 
Closa, J., 1998. The Influence of orbit precision on the quality of ERS SAR interferometric data. 
http://earthl.esrin.esa.it/ORB QL (1 June 1998). 
Graham, L.C., 1974. Synthetic Interferometer Radar for topographic mapping, Proceedings of the I.E.E.E., 62, pp.763- 
768. 
Zebker, H.A., and Goldstein, R.M., 1986. Topographic mapping from interferometric Synthetic Aperture Radar 
observations. Journal of Geophysical Research, 91, pp.4993-4999, 
Zebker, H.A., Werner, C.L., Rosen, P.A., and Hensely, S., 1994. Accuracy of topographic maps derived from ERS-1 
Interferometric Radar. I.E.E.E. Transactions on Geoscience and Remote Sensing, 32(4), 823-836. 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part Bl. Amsterdam 2000. 37