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ASAR Validation Review Geometric Accuracy and Interferometric Applications J ürgen Holzner Remote Sensing Technology Institute German Aerospace Center (DLR). Overview. Objectives Results for the Image Location Accuracy ENVISAT/ ASAR Interferometry. Objectives.
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ASAR Validation Review Geometric Accuracy and Interferometric Applications Jürgen HolznerRemote Sensing Technology InstituteGerman Aerospace Center (DLR)
Overview • Objectives • Results for the Image Location Accuracy • ENVISAT/ ASAR Interferometry
Objectives • ensure optimal image location accuracy • show the feasibility of ENVISAT/ ASAR interferometry
Approach – Image Location Accuracy • determination of the azimuth and range timing offsets. • comparison of predicted and measured positions of strong point targets (transponders, corner reflectors) in slant-range / azimuth co-ordinate system. • predicted positions are obtained with Zero – Doppler iteration.
Netherlands Test Site Results swifterbant (rg x az) mean : 4.10 x 5.42 sigma : 0.11 x 0.30 edam (rg x az) mean: 3.75 x 3.97 sigma: 0.09 x 0.29 zwolle (rg x az) mean : 3.46 x 3.63 sigma : - 48 km aalsmeer (rg x az) mean: 2.97 x 4.10 diff.: 0.27 x 0.39 91 km
Preliminary Results for Other Than IS2 and IS4 Beams and Modes Swifterbant Transponder
Oberpfaffenhofen Test Site Result CR2 (rg x az) 3.40 x 4.43 CR6 (rg x az) 3.36 x 4.45 CR3 (rg x az) 3.74 x 4.87 23 km 32 km
Conclusion on SWST Bias Evaluation (I) • location accuracy transponder/ CR dependent. transponders’/ CRs’ position or internal delay inaccuracies. • transponders Edam and Swifterbant offer consistent time series in accordance with corner reflector results. • range timing offset may be beam dependent. further evaluation necessary!
Conclusion on SWST Bias Evaluation (II) • based on this data a range timingoffset (sampling window start time bias) of (29 ± 3) m is obtained. further monitoring recommended (ascending data sets)! • an azimuth timing offset of (18 ± 4) m is determined based on (restituted/ DORIS orbits). check orbit consistency restituted/ DORIS to predicted! check time correlation pair determination/ accuracy! further monitoring recommended!
ENVISAT/ ASAR Interferometry Results: Las Vegas orbits beam mode temporal baseline spatial perp. baseline height conversion factor coherence range 2092 / 3094 IS 2 IM 70 days 420 m 25 m up to 0.83
timing correction of 4 range samples Differential Interferogram Co-registration
First ENVISAT/ ASAR DEM Las Vegas ( 36.2 N ; 115.2 W ) 181 m 3495 m
Conclusion on ENVISAT/ ASAR Interferometry Results • for Las Vegas test site high coherence even over 70 days was preserved. • high quality interferometric data can be obtained from ENVISAT/ ASAR image mode products. • differential interferogram co-registration verifies proposed range timing correction. • a first DEM based on ENVISAT/ ASAR interferometry was presented.