1. Techniques for High Accuracy Relative and Absolute Localization of TerraSAR-X / TanDEM-X Data U. Balss , M. Eineder, T. Fritz, H. Breit, and C. Minet German Aerospace Center (DLR), Remote Sensing Technology Institute (IMF)

5. Continental Drift and Geodetic Coordinate System s * TSX-1 / TDX-1 orbit in ITRS-2005/08 coordinates * GPS position of CR in tectonic plate fixed system (e.g. ETRS89) misinterpretation of GPS coordinates offset between expected and true CR position (e.g. approx. 60 cm if ETRS89 is taken for ITRF-2005)

6. Effect of Continental Drift on Radar Coordinates (e.g. corner reflector CR moved to northeast) ascending orbit (right looking): CR occurs more in late azimuth and far range than expected t 1 t 2 >t 1 expected position of CR true position of CR flight path continental drift azimuth range W S N E height

7. Effect of Continental Drift on Radar Coordinates (e.g. corner reflector CR moved to northeast) descending orbit (right looking): CR occurs more in early azimuth and near range than expected t 2 <t 1 t 1 expected position of CR true position of CR flight path continental drift azimuth range W S N E height

8. Effect of a Coordinate System Mismatch Wrong: ETRS89 coordinates are misinterpreted as ITRS-2005 Correct: ETRS89 coordinates are transformed to ITRS-2005 system

9. Bistatic Acquisition Geometry of TanDEM-X (Passive Imaging Channel) bistatic range depends on signal travel time which again depends on bistatic range

10. Computation of Bistatic Closest Approach iteration step ( n =0, 1, 2, …) initialization 2) Coordinate of hyperbola apex results by nested intervals . 1) Recursive computation of bistatic range for given slow time t :

12. Absolute Pixel Localization Accuracy of TSX-1 (Based on TSX-1 Calibration Datatakes 2007/09) L1B products created before 2011-07-15: bandwidth dependent range offset: 100 MHz : -33 cm 150 MHz : -14 cm 300 MHz : +12 cm azimuth offset: +8 cm Meanwhile bandwidth dependency is solved by code change in SAR processor and instrument is recalibrated.

13. Absolute Localization Accuracy of TSX-1 (Reprocessed by Actual SAR Processor Version) σ azimuth = 6.3 cm σ range = 3.8 cm The following offsets are subtracted: azimuth offset: +8 cm range offset : -29 cm

14. Absolute Localization Accuracy of TSX-1 and TDX-1 (Based on Calibration Datatakes 2010) TDX-1 σ azimuth = 5.5 cm σ range = 3.5 cm TSX-1 σ azimuth = 5.3 cm σ range = 3.5 cm

15. Relative Localization Accuracy of Bistatic TanDEM-X Acquisitions different scaling of axes azimuth: -100 … +60 mm range : -10 … +6 mm ! mean value: m azimuth = -18 mm m range = -2.1 mm standard deviation: over all acquisitions: σ azimuth = 40 mm σ range = 4.4 mm within an acquisition: σ azimuth = 16 mm σ range = 1.0 mm

17. Thank you for your attention!