InSAR Principles: Guidelines for SAR Interferometry ...

1 TM-19 February 2007 InSAR Principles: Guidelines for SAR Interferometry Processing and Interpretation TM-19 _____ InSAR Principles ii Acknowledgements Authors: Alessandro Ferretti, Andrea Monti-Guarnieri, Claudio Prati, Fabio Rocca Dipartimento di Elettronica ed Informazione, Politecnico di Milano, Italy Didier Massonnet CNES, Toulouse, France Technical coordination: Juerg Lichtenegger ESA/ESRIN (retired), Frascati, Italy Publication: InSAR Principles: Guidelines for SAR Interferometry Processing and Interpretation (TM-19, February 2007) Editor: Karen Fletcher Published and distributed by: ESA Publications ESTEC Postbus 299 2200 AG Noordwijk The Netherlands Tel: +31 71 565 3400 Fax: +31 71 565 5433 Printed in: The Netherlands Price: 40 ISBN: 92-9092-233-8 ISSN: 1013-7076 Copyright: 2007 European Space Agency _____ Table of Contents iii Table of Contents Scope.

2 Viii Part A Interferometric SAR image processing and interpretation 1. Synthetic Aperture Radar A-3 A-3 Introduction to ERS .. A-3 Introduction to A-4 SAR images of the Earth s surface .. A-5 What is a strip-map SAR imaging system?.. A-5 What is a complex SAR image?.. A-6 SAR resolution cell projection on the A-11 2. SAR Interferometry : applications and limits .. A-17 A-17 Terrain altitude measurement through the interferometric phase .. A-18 Interferogram flattening .. A-19 Altitude of ambiguity .. A-20 Phase unwrapping and DEM A-20 Terrain motion measurement: Differential Interferometry .

3 A-23 The atmospheric contribution to the interferometric phase .. A-24 Other phase noise sources .. A-25 Coherence maps .. A-26 3. SAR Differential Interferometry basics and examples .. A-31 A-31 Landers co-seismic deformation .. A-31 Small earthquake modelling .. A-33 The quiet but complicated deformation after an A-35 A case of coherence loss: A-37 A case of damaged raw data, studying a large earthquake in A-38 Part B InSAR processing: a practical approach 1. Selecting ERS images for InSAR processing .. B-3 B-3 Available information about ERS B-3 The ESA on-line multi-mission catalogue .. B-3 B-4 Expected coherence (prototype).

4 B-6 Selecting images for InSAR DEM generation .. B-8 Selecting images for Differential InSAR B-9 2. Interferogram generation .. B-11 TM-19 _____ InSAR Principles iv Generation of synthetic fringes ..B-12 Co-registering ..B-13 Co-registering coefficients ..B-14 Co-registering parameter estimation ..B-16 Implementation of resampling ..B-17 Master and slave Range spectral shift & azimuth common bandwidth filtering ..B-18 Range spectral shift filtering ..B-18 Azimuth common band filtering ..B-20 Interferogram computation ..B-22 Complex multi-looking ..B-24 Generation of coherence maps ..B-26 Applications of coherence.

5 B-27 Interferogram geocoding & mosaicking ..B-29 3. InSAR DEM reconstruction ..B-31 Processing chain and data selection ..B-31 Phase unwrapping techniques for InSAR DEM What are we looking for?..B-34 Case p=2, Unweighted Least Mean Squares method ..B-37 Case p=2, Weighted Least Mean Squares method ..B-38 Case p=1, Minimum Cost Flow Case p=0, Branch-Cut and other minimum L0 methods ..B-39 Outlook ..B-41 From phase to elevation ..B-42 Polynomial approximation of satellite orbits, point localisation and data geocoding ..B-42 Data resampling ..B-45 Impact of baseline errors on the estimated topography.

6 B-45 Precise orbit determination ..B-47 Error sources, multi-baseline strategies and data Multi-interferogram InSAR DEM Combination of ascending and descending passes ..B-53 4. Differential Inteferometry (DInSAR) ..B-57 Examples of differential Interferometry on Physical changes ..B-57 Volcano: Okmok ..B-57 Surface rupture: Superstition Hill ..B-58 Subsidence: East Example of differential Interferometry on ice ..B-62 Review of various criteria for data selection ..B-63 _____ Table of Contents v Interferometric interpretation .. B-63 Interferometry phase signal B-64 Fictitious example interferograms for analysis.

7 B-65 Analysis of fictitious situations .. B-67 Part C InSAR processing: a mathematical approach 1. Statistics of SAR and InSAR C-3 The backscattering process .. C-3 Introduction .. C-3 Artificial backscatterers .. C-3 Natural backscatterers: the spectral shift principle .. C-4 Statistics of the return .. C-7 Interferometric images: C-8 Statistics of coherence estimators .. C-9 Impact of the baseline on coherence .. C-12 Power spectrum of interferometric images .. C-13 Causes of coherence loss .. C-13 Noise, temporal C-13 Volumetric C-13 2. Focusing, Interferometry and slope estimate .. C-15 SAR model: acquisition and C-15 Phase preserving C-15 CEOS offset processing C-18 Interferometric SAR processing.

8 C-18 Spectral shift and common band filtering (revisited).. C-19 DEM generation: optimal slope C-21 Noise sources .. C-24 Processing decorrelation C-25 Examples of decorrelation C-25 3. Advances in phase unwrapping .. C-29 C-29 Residues and charges .. C-31 Effects of noise: pairs of residues, undefined positions of the ghost lines .. C-33 Effects of alias: unknown position of the ghost C-36 Optimal topographies under the Lp C-37 L2, L1, L0 optimal topographies .. C-37 Slope C-40 Removal of low resolution estimates of the topography .. C-41 Bias of the slope C-41 Analysis in the wave-number C-42 L2 optimisation in the wave-number domain.

9 C-42 Weighting factors in the optimisation .. C-43 TM-19 _____ InSAR Principles vi 4. Multiple image combination for DEM generation and ground motion estimation ..C-45 Multi-baseline phase unwrapping for InSAR topography Applications to repeat-pass Interferometry ..C-48 Example 1: the Vesuvius data set ..C-50 Example 2: The Etna data The Permanent Scatterers technique ..C-56 Space-time estimation ..C-58 Subsidence in Pomona ..C-59 Ground slip along the Hayward fault ..C-62 Seasonal deformation in the Santa Clara 5. Applications based on spectral shift ..C-65 Introduction to spectral shift ..C-65 Interferometric quick look (IQL).

10 C-67 6. Differential Interferometry ..C-71 Differential Interferometry using an available DEM ..C-72 Differential Interferometry with three or more combined images ..C-77 Techniques to avoid phase unwrapping ..C-79 Integer combination ..C-79 Interferogram stacking ..C-82 Information contained in interferometric measurements ..C-83 Residual orbital fringes ..C-83 Uncorrected Heterogeneous Heterogeneous ionosphere ..C-87 Static atmosphere ..C-88 Radar clock drift ..C-88 7. Envisat-ASAR interferometric techniques and applications ..C-91 ScanSAR: an introduction.