Validation and quality control for InSAR using trihedral radar reflectors Delft University of Technology Petar Marinkovic, Gini Ketelaar, Freek van Leijen, Ramon Hanssen DEOS: Delft Institute of Earth Observation and Space Systems January 16, 2008
Delft test site: impressions January 2004 leveling 2
Agenda Objective and motivation: • what is the quality of point scatterer phase observation in PSI? Delft test site: • corner reflector experiment • defo. monitoring under controlled circumstances Validation strategy and results: • leveling vs. InsAR vs. PSI Conclusions 3
Leveling vs. InSAR CR4-CR5 CR4-CR3 ASAR ERS Leveling 4
Leveling vs. InSAR: a posteriori 1sigma CR4-CR5 CR4-CR3 ASAR Leveling ERS 5
Leveling vs. InSAR: a posteriori 1sigma 1Sigma_ASAR= 1.6 mm 1Sigma_ERS2 = 2.8 mm CR4-CR5 CR4-CR3 ASAR Leveling ERS 6
Delft test site 7
Delft test site: leveling network ● surveys every ~35 days ~200m ● high precision leveling ● redundant network CR#5 ● adjustment and outlier removal Bn#2 ● since Aug.2005 ground water CR#4 measurements CR#3 Bn#1 8
Delft test site: CR heights ground watter measurements correlate with leveling ~95% CR3 CR5 CR4 9
Delft test site: InSAR data [ASAR] 10
Delft test site: InSAR data [ERS2] ERS2: high fDC! 11
Delft test site 12
Validation strategy: Leveling vs. InSAR “fixed” InSAR estimates: Leveling estimates: ● redundant network/measurements ● unwrapped wrt. leveling ● converted to vertical ● adjustment and testing ● a.posteriori 1sigma of dd ~ 1.5mm ● full VC matrix ● “connection matrix” ● “mature” technique ● SCR (signal to clutter) Mathematical framework: Analysis output: ● analysis of residuals (leveling – InSAR) • 1sigma of InSAR.dd ● constrained adjustment deformation measurements ● outlier removal • a.posteriori “error bars” ● VCE (variance component estimation) 13
Leveling vs. InSAR : “raw” 1Sigma_ASAR= 2.4 mm 1Sigma_ERS2 = 10.7 mm CR4-CR5 CR4-CR3 14 ASAR ERS Leveling
Doppler variations of ERS2 15
Influence of viewing geometry azimuth ...compensates for unaccounted reference phase computation reference of “flat-earth phase” ground range actual location of point target reference of interferometric phase 16
Influence of viewing geometry azimuth ...compensates for unaccounted reference phase computation reference of “flat-earth phase” ground range actual location of point target reference of interferometric phase sub.pixel correction: • azimuth: delta fDC dependence • range: Bperp dependence 17
Doppler variations of ERS2 18
Leveling vs. InSAR : “raw” 1Sigma_ASAR= 2.4 mm 1Sigma_ERS2 = 10.7 mm CR4-CR5 CR4-CR3 19 ASAR ERS Leveling
Leveling vs. InSAR : sub.pixel corrected 1Sigma_ASAR= 1.7 mm 1Sigma_ERS2 = 6.9 mm CR4-CR5 CR4-CR3 20 ASAR ERS Leveling
Doppler ambiguities? Doppler centroid -2*PRF +2*PRF CR3-CR4: difference InSAR vs levelling 21
Leveling vs. InSAR : sub.pixel corrected CR4-CR5 CR4-CR3 22 ASAR ERS Leveling
Leveling vs. InSAR : sub.pixel.no.outliers.doppler 1Sigma_ASAR= 1.6 mm 1Sigma_ERS2 = 2.8 mm CR4-CR5 CR4-CR3 ASAR ERS Leveling 23
a.posteriori 1sigma of dd InSAR phase - with outlier removal - ERS2 ASAR no sub-pixel correction 4.5 mm 2.4 with sub-pixel correction 2.9 1.6 with sub-pixel and fDC correction 2.8 1.6 - without outlier removal - ERS2 ASAR no sub-pixel correction 10.7 2.4 with sub-pixel correction 6.9 1.7 with sub-pixel and fDC correction 4.1 1.7 24
Leveling vs. InSAR: a posteriori 1sigma CR4-CR5 CR4-CR3 ASAR Leveling ERS 25
Connection to the natural PS 26
Connection to natural PS • linear velocities estimated together with periodic signal 27
Natural PS vs Leveling ground watter measurements PSI Leveling CR3 CR5 CR4 28
Natural PS vs Levelling vs InSAR CR4-CR5 CR4-CR3 ASAR Leveling PSI 29
Conclusions • empirical 1sigma of InSAR deformation estimates: • ERS2 (high.doppler.data): ~ 2.8 mm along the vertical • ASAR : ~ 1.6 mm along the vertical • Note: ASAR in the same level of accuracy as leveling! 30
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