TH1.L09 - ACCURATE FOCUSING OF SINGLE-PASS AIRBORNE INSAR DATA AT L-BAND

Accurate Focusing of Single-Pass Airborne InSAR Data at L-band

IGARSS 2010

Honolulu, Hawaii, July 26 - 30, 2010

Marcus Schwäbisch, Bryan Mercer, Qiaoping Zhang, Wei HuangIntermap Technologies

© 2008 Intermap Technologies. All rights reserved.2

Overview

Motivation

Investigated Focusing Options Omega-k and dual-line mocomp vs. single-line mocomp

Time domain backprojection

Performance Evaluation Focusing

Mis-registration

Squint handling

PolInSAR

Conclusion


Motivation

Goal accurate products from an airborne long-wavelength polarimetric

interferometric SAR in an operational scenario» Intermap’s TopoSAR L-band single-pass PolInSAR

Processing challenges airborne: motion compensation long wavelength: wide azimuth beamwidth, long integration time interferometry: differential phase accuracy PolInSAR: requires high resolution processing to achieve sufficient number

of looks operational aspect: requires high squint capability

Processing aspects azimuth focusing motion compensation


Investigated processing options

Omega-k focusing with single-line mocomp Omega-k in principle is an optimum SAR focusing technique without

approximations requires data to be acquired along a straight line single-line mocomp is fast and efficient, but non-optimal for significant

InSAR baselines

Omega-k focusing with dual-line mocomp dual-line mocomp avoids differential effects in interferometric channels center-beam approximation in mocomp still does not avoid focusing degradation caused by FM rate errors

Time domain backprojection with integrated mocomp full-aperture solution for mocomp terrain dependent time consuming


Single-line vs. dual-line motion compensation

FM rate mismatch is being caused whenever the APC position deviates from the straight line requirementleads to defocusing and phase corruptionproblem in frequency-domain focusing: biases can be compensated, but instantaneous displacements not


Analysis

Experimental setup L-band single-pass test data from Intermap’s experimental

TopoSAR platform

various testsites in Western Canada

Performance evaluation focusing performance

interferometric performance» channel mis-registration

» coherence

high squint handling

PolInSAR performance


TopoSAR single-pass L-band platform

< -40dBNESZ

3.5 minterferometric baseline

1.2 kmswath width

1000 mtypical flight altitude

0.25 mazimuth resolution

up to 1.1 mrange resolution

up to 135 MHz

(80 MHz nominally)

max. system bandwidth

2200 HzPRF (per channel)

quad (HH, HV, VH, VV)

Polarization

0.2262 mWavelength

0.4 kWPeak power

log-periodic antenna


L-band Pauli Decomposition

Didsbury, AB, Canada

0.25m az resolution

1m resolution @ 4 looks


Corresponding Google Earth image


Analysis

Experimental setup L-band single-pass test data from Intermap’s experimental

TopoSAR platform

various testsites in Western Canada

Performance evaluation focusing performance

interferometric performance» channel mis-registration

» coherence

high squint performance



Focusing performance

single-line mocomp

impulse response

0.5 m resolution

3.5° squint



dual-line mocomp

impulse response

0.5 m resolution

3.5° squint



time domain

impulse response

0.5 m resolution

3.5° squint


High resolution processing

0.25 m azimuth resolution (> 8 sec azimuth integration time)

single-line mocomp dual-line mocomp time domain



Channel mis-registration (azimuth)

mis-registration in azimuth

20% oversampling (sample size = 0.8 × resolution cell size)

-1 samples 1


Coherence


single-pol coherence (HH)


High squint handling

impulse response for 9.5° squint angle, 0.5 m az resolution




Edson, AB, Canada

forest height and ground topography estimation

RVoG model

PolInSAR derived tree height

PolInSAR derived ground topography

Air photo

Profile 1

108510901095

110011051110

111511201125

1130113511401145

0 100 200 300 400 500 600

Cross Section

Meter

s

Meters

Lidar h100

Lidar DTM

L-band tree height

L-band ground


Summary and Conclusions

We have analyzed various focusing/mocomp options to accurately process single-pass airborne PolInSAR data at L-band

Omega-k focusing with dual-line mocomp and center-beam approximation is sufficient for moderate resolution and moderate platform motion

Time domain backprojection with terrain-based mocomp greatly improves the performance for high-res and high squint applications

Future steps system re-calibration (geometric and polarimetric) PolInSAR performance evaluation speed up the time domain implementation

» fast backprojection techniques» GPU processing

TH1.L09 - ACCURATE FOCUSING OF SINGLE-PASS AIRBORNE INSAR DATA AT L-BAND

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