This paper presents a novel method for estimating the absolute phase offset in interferometric synthetic aperture radar (SAR) measurements for digital elevation model (DEM) generation. The method is based on “phase-offset functions (POF),” relating phase offset to topographic height, and are computed for two different overlapping interferometric data acquisitions performed with considerably different incidence angles over the same area of interest. For the purpose of extended mapping, opposite viewing directions are preferred. The two “phase-offset functions” are then linearly combined, yielding a “combined phase-offset function (CPOF)”. The intersection point of several straight lines (CPOFs), corresponding to different points in the overlap area allows for solving the phase offset for both acquisitions. Aiming at increasing performance and stability, this intersection point is found by means of averaging many points and applying principal component analysis. The method is validated against traditional phase offset estimation with corner reflectors (CR) using real OrbiSAR-1 data in X- and P-band.
References
[1]
Graham, L.C. Synthetic interferometer radar for topographic mapping. Proc. IEEE 1974, 62, 763–768.
[2]
Zebker, H.A.; Goldstein, R.M. Topographic mapping from interferometric synthetic aperture radar observations. J. Geophys. Res 1986, 91, 4993–4999.
[3]
Hagberg, J.O.; Ulander, L.M.H. On the optimization of interferometric SAR for topographic mapping. IEEE Trans. Geosci. Remote Sens 1993, 31, 303–306.
Ghiglia, D.C.; Romero, L.A. Robust two-dimensional weighted and unweighted phase unwrapping that uses fast transforms and iterative methods. J. Opt. Soc. Am 1994, 11, 107–117.
[7]
Fornaro, G.; Franceschetti, G.; Lanari, R. Interferometric SAR phase unwrapping using Green’s formulation. IEEE Trans. Geosci. Remote Sens 1996, 34, 720–727.
[8]
Pritt, M.D. Phase unwrapping by means of multigrid techniques for interferometric SAR. IEEE Trans. Geosci. Remote Sens 1996, 34, 728–738.
[9]
Madsen, S.N. Absolute phase determination techniques in SAR interferometry. Proc. SPIE 1995, 2487, 393–401.
[10]
Scheiber, R.; Fischer, J. Absolute Phase Offset in SAR Interferometry: Estimation by Spectral Diversity and Integration into Processing. Proceedings of EUSAR, Ulm, Germany, 25–27 May 2004.
[11]
Brcic, R.; Eineder, M.; Bamler, R. Absolute Phase Estimation from TerraSAR-X Acquisitions using Wideband Interferometry. Proceedings of IEEE Radar Conference, Pasadena, CA, USA, 4–8 May 2009.
[12]
Eineder, M.; Adam, N. A maximum likelihood estimator to simultaneously unwrap, geocode and fuse SAR interferograms from different viewing geometries into one digital elevation model. IEEE Trans. Geosci. Remote Sens 2005, 43, 24–36.
[13]
Fornaro, G.; Sansosti, E.; Lanari, R.; Tesauro, M. Role of processing geometry in SAR raw data focusing. IEEE Trans. Aerosp. Electron. Syst 2002, 38, 441–454.
[14]
Schreier, G. Standard Geocoded Ellipsoid Corrected Images. In SAR Geocoding: Data and Systems. Chapter 6; Wichmann Verlag: Kalsruhe, Germany, 1993; pp. 159–163.
[15]
Maragos, P. Morphological Filtering for Image Enhancement and Feature Detection. In Handbook of Image and Video Processing, 2nd ed.; Bovik, A.C., Ed.; Academic Press: New York NY, USA, 2005; pp. 135–156.
[16]
Pinheiro, M.; Rosa, R.; Moreira, J.R. Multi-Path Correction Model for Multi-Channel Airborne SAR. Proceedings of 2009 IEEE International Geoscience & Remote Sensing Symposium (IGARSS’09), Cape Town, South Africa, 12–19 June 2009; 3, pp. 729–732.
[17]
Taylor, J.R. An Introduction to Error Analysis: The Study of Uncertainties in Physical Measurements, 2nd ed. ed.; University Science Books: Sausalito, CA, USA, 1997.
[18]
Richards, J.A.; Jia, X.P. Multispectral Transformation of Image Data. In Remote Sensing Digital Image Analysis, 2nd ed. ed.; Springer-Verlag: Berlin, Germany, 1993; pp. 137–163.
[19]
Rodriguez, E.; Martin, J.M. Theory and design of interferometric synthetic aperture radar. IEE Proc.-F 1992, 139, 147–159.
[20]
Greenwalt, C.R.; Schultz, M.E. Principles and Error Theory and Cartographic Applications. ACIC Thechnical Report No 96; Aeronautical Chart and Information Center: St. Louis, MO, USA, 1968.
