3D Geo-location Error of Radar Pixels: Modeling, Propagation and Mitigation
Dheenathayalan, Prabu1; Schubert, Adrian2; Small, David2; Hanssen, Ramon1
1Department of Geoscience and Remote Sensing, Delft University of Technology, NETHERLANDS; 2Remote Sensing Laboratories, University of Zurich, SWITZERLAND

Absolute geo-location accuracy of TerraSAR-X SAR pixels, after compensating atmosphere and tidal effects, was reported in [1,2,3] to be in the order of a few centimeters in azimuth and range directions, validated by measuring the phase centers of trihedral corner reflectors (CR) with differential GPS instruments to centimeter accuracy and predicting their respective positions in the radar image.

Here we exploit time-series Interferometric SAR (InSAR) to enhance the geolocation capability in three dimensions viz. azimuth, range, and cross-range. The cross-range dimension is obtained from the InSAR observations. 3D positioning and its uncertainty are modeled as an ellipsoidal confidence interval centered at the estimated position, with its semi-principal axes in azimuth, range and cross-range. This methodology is sensor independent.

We demonstrate our 3D geo-location modeling for coherent pixels. The error ellipsoids in radar geometry for these PS are then propagated during geocoding into a local geodetic datum geometry, with Northing (N), Easting (E) and Height (H) coordinates. The geocoded error ellipsoid in the map geometry improves our ability to link radar reflections to real world objects [4,5]. Atmospheric path delay and tidal effects are computed and propagated for the coherent targets. Towards this goal, TerraSAR-X satellite images over urban areas in the Netherlands are used. For mitigation of the atmospheric path delay component, the permanent GPS network of the Netherlands is exploited.


[1] Schubert A., M. Jehle., D. Small, and E. Meier, ''Influence of Atmospheric Path Delay on the Absolute Geolocation Accuracy of TerraSAR-X High-Resolution Products,'' IEEE Transactions on Geoscience and Remote Sensing, 48(2),pp. 751-758, Feb. 2010.

[2] Schubert A., M. Jehle., D. Small, and E. Meier, ''Mitigation of atmospheric perturbations and solid-Earth movements in a TerraSAR-X time-series,'' J. of Geodesy, 86(4), DOI 10.1007/s00190-011-0515-6, pp. 257-270, 2012.

[3] Eineder M., C. Minet, P. Steigenberger, X. Cong , and T. Fritz, ''Imaging Geodesy - Toward centimeter-level ranging accuracy with TerraSAR-X,'' IEEE Transactions on Geoscience and Remote Sensing, 49(2), pp. 661-671, Feb. 2011.

[4] Prabu Dheenathayalan and Ramon Hanssen. Target characterization and interpretation of deformation using persistent scatterer interferometry and polarimetry. In 5th International Workshop on Science and Applications of SAR Polarimetry and Polarimetric Interferometry, 'POLInSAR 2011', Frascati, Italy, 24-28 Jan 2011, 2011.

[5] Prabu Dheenathayalan, Miguel Caro Cuenca, and Ramon Hanssen. Different approaches for psi target characterization for monitoring urban infrastructure. In In 8th InternationalWorkshop on Advances in the Science and Applications of SAR Interferometry, 'FRINGE 2011', Frascati, Italy,19-23 Sep 2011.