Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit

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1 INTERGEO 2011 Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit Michael Eineder, N. Yague-Martinez, C. Minet, X. Cong, B. Schättler DLR Institut für Methodik der Fernerkundung

2 Outline Goal: Capture earth surface motion globally from space with high accuracy and resolution Differences between InSAR and high resolution image correlation techniques (HRIC) Error sources & recent correction techniques turning space borne imaging Synthetic Aperture Radar (SAR) systems into geodetic measurement devices Examples M. Eineder, Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit INTERGEO

3 InSAR Versus Image Correlation InSAR Image Correlation Massonnet et al., The displacement field of the Landers earthquake mapped by radar interferometry, Nature, V.364, p , 1993 Prinziple: Coherent pixel phase (no contrast needed) Properties high spatial resolution ( m) high accuracy ( λ/10) 1D, ambiguous, relative Eineder, Wael Abdel Jaber, Glacier Flow and Topography Measurements with TerraSAR-X and TanDEM-X, IGARSS 2011 Prinziple: Inter pixel contrast (needs window/edge) Properties lower spatial resolution ( m x 10) Lower accuracy (cm) 2D, absolute M. Eineder, Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit INTERGEO

4 Error Source: Satellite Orbits Characteristics: Large scale (smooth) offsets < 5 centimeters Consequences: InSAR: Phase offsets (invisible) Phase ramps motion error gradients Overall location error (small) HRIC: Offsets Ramps (comparatively small) Overall location error (small) Compensation: InSAR: Offset control point (anyway) Ramp control points loss of information HRIC: Offset & ramp control points loss of information M. Eineder, Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit INTERGEO

5 Error Source: Reference Frames and Earth Tides Characteristics: Shifts up to ±20 centimeters Orbit Error ITRF e.g. ETRF Consequences: InSAR: Invisible phase offsets HRIC: Offsets (visible) Overall location error (small) M. Eineder, Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit INTERGEO

6 Error Source: Earth Tides Compensation: InSAR: unnecessary because local relative measurement HRIC: Use of model Honolulu, July 31th, Deformation [m] : AM 2:24 AM 4:48 AM 7:12 AM 9:36 AM 12:00 PM 2:24 PM 4:48 PM 7:12 PM 9:36 PM 12:00 AM Up North East Daytime [UTC] M. Eineder, Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit INTERGEO

7 Error Source: Atmosphere Characteristics: Distance dependent turbulences from mm up to ±15 cm Variograms Consequences: InSAR: Phase offsets (invisible) stddev [mm] Phase patterns dangerous motion errors HRIC: Distance [km] Offsets (visible) Hanssen, Netherlands Wadge, Lanyi Meyer, Warsaw Parizzi, Berlin-C Parizzi, Berlin-X Motion patterns (comparatively small) Overall location error (small) M. Eineder, Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit INTERGEO

8 Error Source: Atmosphere Compensation: InSAR: (Goal: mm/year) 1. Temporal averaging Persistent Scatterer Interferometry (state of the art, expensive) 2. High resolution weather (H 2 O) modelling (future, not yet operational) HRIC: (Goal: cm/year) 1. Large area compensation by GPS Trop. Zen. Delay or 2. or low resolution weather model (new!) or 3. high resolution weather model (future, not yet operational) M. Eineder, Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit INTERGEO

9 ZDP from EUREF Permanent GPS Network Wettzell, Bad Kötzting, Germany (WTZR) M. Eineder, Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit INTERGEO

10 Path Delay from Numerical Weather Model Data ERA-Interim reanalysis from European Centre for Medium-Range Weather Forecasts (ECMWF) Horizontal resolution: full T255 spectral truncation (grid size ~80 km) Available on 0h, 06h, 12h and 18h, since 1989 to current 3 months p atmo p i p 0 M. Eineder, Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit INTERGEO

11 Comparison GPS ZDP with ECMWF STD STD STD STD STD STD STD STD STD STD STD 8.7 STD 12.9 STD 7.7 STD 13.0 STD 13.0 M. Eineder, Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit INTERGEO

12 Summary: Current Status in HRICT Accuracy Monitoring of 6 corner reflectors with known position and 22 TerraSAR-X acquisitions (100 MHz, 150 MHz and 300 MHz) Ascending & descending orbits, incidence angle from: 21 to 58 Compensation of solid Earth tides, tropospheric delay and continental drifts Residual Range Delay with ECMWF SDP Correction STD [cm] 100 MHZ MHZ MHZ azimuth offset [m] MHz 150 MHz 300 MHz -0.2 range offset [m] M. Eineder, Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit INTERGEO

13 Example 1: Tohoku Earthquake descending co-seismic image pairs spread over the archipelago stripmap mode (30 x 50 km) single acquisitions not possible to derive 3D vectors hor. projection on ground Sendai M. Eineder, Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit INTERGEO

14 Co-seismic HRIC Displacement Map at Sendai rg az M. Eineder, Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit INTERGEO

15 Co-seismic Displacements from GPS and from SAR SAR GPS Acknowledgement: Co-seismic displacement from GPS by GEONET. Prof. Hashimoto. M. Eineder, Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit INTERGEO

16 Conclusions SAR interferometry is an established method for DEM generation and relative subsidence measurements (Persistent Scatterer Interferometry) with ambiguity problems provides only relative measurements High resolution image correlation techniques with novel geodetic corrections provide absolute distances with centimeter accuracy and avoid phase ambiguity problems deliver 2D motion vectors Goal/potential: reach millimeter accuracy absolute M. Eineder, Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit INTERGEO

17 Example 2: Glacier Velocity Measurements Average Three-Year Velocity Map Drygalski Glacier, Antarctica 6.0 [m/d] km C A M. Eineder, Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit INTERGEO

18 Temporal Velocity Profile at Point C 1,20 1,15 Velocity [m/d] 1,10 1,05 1,00 0,95 Summer Winter Summer Winter Summer Winter 0,90 0,0 0,5 1,0 1,5 2,0 2,5 3,0 Time [years] - 08-OCT-2007 Measurements confirm error margin (residuals stdev. < 2 cm d -1 ) slight seasonal variations, maybe decelleration M. Eineder, Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit INTERGEO

19 Glacier Acceleration Measurements Average Three-Year Acceleration Map Drygalski Glacier, Antarctica 0.4 [md -1 a -1 ] -0.4 C A M. Eineder, Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit INTERGEO

20 M. Eineder, Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit INTERGEO

21 Alaska M. Eineder, Geodätische Messungen mit TerraSAR-X - Stand der Genauigkeit INTERGEO