ALTAMIRA INFORMATION
Combination of X-band high resolution SAR data from different sensors to produce ground
deformation maps
Javier Duro, Marc Gaset, Fifame Koudogbo, Alain Arnaud Altamira Information
Frascati, September 2011
Combination of X-band high resolution SAR data from different sensors to produce ground deformation maps
Problem definition
LOS
• Objective
to detect and follow-up unstable areas in steep slopes
• High revisit time was require
• Characteristics of the Area of interest• Arid terrain good radar
backscattering high density of distributed-targets like pixels
• Mountainous area geometric distortions
• Program TerraSAR-X data conflicts with TanDEM-X mission
• We completed the archive with COSMO-SkyMed data
x x x x
X cancelled acquisition
Participation in Terrafirma
Overview of combination of sensors in InSAR applications
Principle for combination of sensors
Example of combination of sensors
Conclusions
Agenda
The continuity of the PSI monitoring is ensured by the new sensors
Overview of combination of sensors in InSAR applications Overview of available spaceborne SAR sensors: Past, Present and Future
European Space Agency (ESA)
1992-2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020
Canadian Space Agency (CSA)
German Space Agency (DLR) –EADS –Infoterra GmbH
Radarsat-1
Radarsat-2
ERS-1
Envisat
ERS-2
Sentinel-1
Seosar
TerraSAR-X
Tandem-X
TerraSAR-X 2
ItalianSpace Agency (ASI) Cosmo
SKYMED
Japanese Space Agency (JAPEX) JERS-1
ALOS L-BAND
C-BAND
X-BAND
European Space Agency (ESA)
1992-2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020
Canadian Space Agency (CSA)
German Space Agency (DLR) –EADS –Infoterra GmbH
Radarsat-1
Radarsat-2
ERS-1
Envisat
ERS-2
Sentinel-1
Seosar
TerraSAR-X
Tandem-X
TerraSAR-X 2
ItalianSpace Agency (ASI) Cosmo
SKYMED
Japanese Space Agency (JAPEX) JERS-1
ALOS L-BAND
C-BAND
X-BAND
The continuity of the PSI monitoring is ensured by the new sensors
First opportunity to merge with ERS1 and ERS2 straightforward because both sensors are identical:
• Same orbital path
• Same carrier frequency (F0 FM, PRF)
• Same acquisition mode
No constraint in the combination opportunities
Overview of combination of sensors First opportunity to merge SAR data from different sensors
European Space Agency (ESA)
1992-2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020
Canadian Space Agency (CSA)
German Space Agency (DLR) –EADS –Infoterra GmbH
Radarsat-1
Radarsat-2
ERS-1
Envisat
ERS-2
Sentinel-1
Seosar
TerraSAR-X
Tandem-X
TerraSAR-X 2
ItalianSpace Agency (ASI) Cosmo
SKYMED
Japanese Space Agency (JAPEX) JERS-1
ALOS L-BAND
C-BAND
X-BAND
The continuity of the PSI monitoring is ensured by the new sensors
Second opportunity to merge data from different sensors with different
characteristics with ERS and ENVISAT not straightforward because:
• Slightly different carrier frequencies (~31MHz)
• Different acquisition mode
Some constraint in the combination opportunities
Overview of combination of sensors Second opportunity to merge SAR data from different sensors
Overview of combination of sensors First demonstration of cross-interferometry in 2003 under ESA
contract 16702/02/ILG
Limitation due to the volumetric decorrelation given by the reduced height of ambiguity
A. Arnaud, N. Adam, R. Hanssen, J. Inglada, J. Duro, J. Closa, and M. Eineder. “ASAR-ERS interferometric phase continuity”. IGARSS, 21-25 July 2003.
ERS-ENVISAT cross-interferogram over the Las Vegas area
produced by DLR
ERS-ENVISAT cross-interferogram over Paris produced by
ALTAMIRA INFORMATION
J. Duro, J. Inglada, J. Closa, N. Adam, and A. Arnaud. “High resolution differential interferometry using time series of ERS and ENVISAT SAR data”. FRINGE 2003, 1-5
December 2003
Maps of geocoded mean subsidence for ERS1-2 and for ASAR
-5
-4
-3
-2
-1
0
1
2
1998 1999 2000 2001 2002 2003 2004 2005
cm
-5
-4
-3
-2
-1
0
1
2
1998 1999 2000 2001 2002 2003 2004 2005
cm
time series of detected ground motion merging -
ERS1/2
-
ASAR
data in the same PSI processing
-6
-5
-4
-3
-2
-1
0
1
2
1998 1999 2000 2001 2002 2003 2004 2005
cm
with in-situ validation
Overview of combination of sensors First opportunity to merge SAR data from different sensors with
different characteristics
European Space Agency (ESA)
1992-2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020
Canadian Space Agency (CSA)
German Space Agency (DLR) –EADS –Infoterra GmbH
Radarsat-1
Radarsat-2
ERS-1
Envisat
ERS-2
Sentinel-1
Seosar
TerraSAR-X
Tandem-X
TerraSAR-X 2
ItalianSpace Agency (ASI) Cosmo
SKYMED
Japanese Space Agency (JAPEX) JERS-1
ALOS L-BAND
C-BAND
X-BAND
The continuity of the PSI monitoring is ensured by the new sensors
RSAT1 with RSAT2. Not straightforward. Even worst that in the case of ERS/ENVISAT
•Same orbital path Radarsat1 is not yaw-steered and has less precise orbits
•Different carrier frequencies (F0 , PRF, FM )
•Same acquisition modes
Overview of combination of sensors New combination opportunities with the present sensors?
European Space Agency (ESA)
1992-2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020
Canadian Space Agency (CSA)
German Space Agency (DLR) –EADS –Infoterra GmbH
Radarsat-1
Radarsat-2
ERS-1
Envisat
ERS-2
Sentinel-1
Seosar
TerraSAR-X
Tandem-X
TerraSAR-X 2
ItalianSpace Agency (ASI) Cosmo
SKYMED
Japanese Space Agency (JAPEX) JERS-1
ALOS L-BAND
C-BAND
X-BAND
The continuity of the PSI monitoring is ensured by the new sensors
Overview of combination of sensors New combination opportunities with the present sensors?
TSX with TDX. Sensors of identical
characteristics
•Same orbital paths
•Same carrier frequencies (F0 , PRF, FM )
•Same acquisition modes
CSK1 with 2, 3 and 4. Sensors of identical characteristics
•Same orbital paths
•Same carrier frequencies (F0 , PRF, FM )
•Same acquisition modes
•Slightly different Doppler centroids
Cosmo SKYMED
European Space Agency (ESA)
1992-2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020
Canadian Space Agency (CSA)
German Space Agency (DLR) –EADS –Infoterra GmbH
Radarsat-1
Radarsat-2
ERS-1
Envisat
ERS-2
Sentinel-1
Seosar
TerraSAR-X
Tandem-X
TerraSAR-X 2
ItalianSpace Agency (ASI) Cosmo
SKYMED
Japanese Space Agency (JAPEX) JERS-1
ALOS L-BAND
C-BAND
X-BAND
The continuity of the PSI monitoring is ensured by the new sensors
TSX with CSK. Not straightforward.
•Different orbital path
•Different carrier frequencies (F0 , PRF, FM )
•Different acquisition modes
Overview of combination of sensors New combination opportunities with the present sensors?
Overview of combination of sensors in InSAR applications
Principle for combination of sensors
Example of combination of sensors
Conclusions
Agenda
Principle for the combination of sensors in PSI processing Sensors combination options
Exploit cross-interferograms Merge sub-stacks of interferograms
Precise coregistration is required to deal with large baselines and different resolutions
Benefits• Real measure of ground motion
Drawbacks• Combinations opportunities are limited due to the common bandwidth (not adequate baseline values Vs wavelength change)• Severe affectation of the volumetric decorrelation• Variant SNR in function of the local slope along the swath
Complex adaptive filters to enhance the SNR over distributed targets
Each slope orientation and angle would require a specific baseline value to have common bandwidth
Benefits• Simple processing• Keep the SNR• More suitable for distributed targets
Drawbacks• It require an artificial bridge to calibrate the time series obtained for the two sensors
Principle for the combination of sensors in PSI processing Selection of the optimum CSK acquisition geometry
• Option A) using cross-interferograms Given a difference of 50 MHz in the carrier frequency and an incidence angle of 35º, the
common bandwidth is maximized when:
for flat terrain ( ) a perpendicular baseline of -2200 m is required to compensate this spectral shift
In our example, to have this perpendicular baseline the incidence angle of the Cosmo acquisitions must be of about 25º not useful to perform cross-interferometry
)tan(0
0
RBf
f perpTSX
0
CSK TSXSampling
Freq. 112.50 MHz 109.89 MHzPRF 3061.22 Hz 3704.36 HzF0 9.60 GHz 9.65 GHz
Lambda 0.03125 0.03109Incidence ? 35.26º
Azimuth res. 2.3 m 1.9 mRange res. 1.3 m 1.3 m
R0 792 Km 614 Km
TSX and CSK range spectrum overlap at 0 baseline Sensors main parameters
CSK TSXSampling
Freq. 112.50 MHz 109.89 MHzPRF 3061.22 Hz 3704.36 HzF0 9.60 GHz 9.65 GHz
Lambda 0.03125 0.03109Incidence 40º 35º
Azimuth res. 2.3 m 1.9 mRange res. 1.3 m 1.3 m
R0 792 Km 614 Km
Sensor main parameters
• Option B) merging interferograms of different sub-stacksThe CSK acquisition with similar incidence angle (40º) was selected to minimise the
geometric distortions and the radar backscattering differences
The perpendicular for this acquisitions was of 156 Km with respect to the TSX orbits
Considering the local slope of the area of interest the resulting spectral shift > 1 GHz 30α
TSX and CSK range spectrum overlap at Bperp
= 156Km and
We expect to have the same distributed-scatterers like pixels in both sub-stacks due to the similar acquisition geometries and sensor characteristics
Principle for the combination of sensors in PSI processing Selection of the optimum CSK acquisition geometry
30α
LOS
• Accurate coregistration procedure To compensate image distortions due to the high baseline and the important topography
• Identify the natural targets that give coherent measurements in both data- stacks final density of measurement points will be decreased?
• Define a calibration rule for both sub- stacks
constraint in the equation system that retrieve the Time Series to force the same ground motion for these two dates
Principle for the combination of sensors in PSI processing Key points
156K
m b
asel
ine
Principle for the combination of sensors in PSI processing PSI processing approach used in this case
Optimum CSK SM geometry selection
Coregistration to CSK SM
CSK images TSX images
CSK-CSK
interferograms
TSX-TSX
interferograms
SPNCoherent point selection with merged
stacks of interferograms
Use calibration rule to produce Time Series
ATMOTOPOINT ˆ
Overview of combination of sensors in InSAR applications
Principle for combination of sensors
Example of combination of sensors
Conclusions
Agenda
Example of combination of sensors Cross-sensor coregistration quality check
TSX images have been coregistered to CSK geometry
RGB amplitude image shows the coregistration quality: Green and blue colors are CSK / Red is TSX
The coregistration quality is good except in layover areas the distorsions are too big and the resolution too poor
The radar backscattering is very similar in most of the areas
The change in the image geometries does not affect the interferogram quality
TSX-TSX interferometric
coherence [0:1]
•In its own geometry
Mean: 0.602
Stddev: 0.242
•In CSK geometry
Mean: 0.561
Stddev: 0.249
Example of combination of sensors Cross-sensor coregistration quality check
Example of combination of sensors Identification of common coherent areas in both data-stacks
Interferograms with similar characteristics show areas with the same quality
Example of combination of sensors Identification of common coherent areas in both data-stacks
• The quality of the topographic model adjustment decreases slightly when adding the TSX data to the CSK stack we lose 10% of the measurement points at 0.75 of coherence
• We can identify areas where the model coherence increases and areas were decreases it is difficult to retrieve an
apparent correlation with the local slope:• Donwslope angles on areas where the quality decreases: mean: -25º, stdev: 9º• Donslope angles on areas where the quality increases: mean: -32º, stdev: 10º
The slight decreasing of the height estimation quality must be caused by geometric decorrelation due the 5º
of incidence angle difference between sensors.
Model coherence histogram with only CSK-CSK combinations
estimated mean value 0.678
Model coherence histogram with CSK-CSK and TSX-TSX combinations
estimated mean value 0.616
+2.0 a +3.5
-2.0 a -3.5
+2.0 a -2.0
Acummulated
displacement (cm)
More than -5.0
-3.5 a -5.0
+3.5 a +5.0
More than +5.0
Subs
iden
ce
Upl
ift
Example of combination of sensors SPN movement detection
Example of combination of sensors SPN movement detection
+2.0 a +3.5
-2.0 a -3.5
+2.0 a -2.0
Acummulated
displacement (cm)
More than -5.0
-3.5 a -5.0
+3.5 a +5.0
More than +5.0
Subs
iden
ce
Upl
ift
Example of combination of sensors SPN movement detection Time Series
Overview of combination of sensors in InSAR applications
Principle for combination of sensors
Example of combination of sensors
Conclusions
Agenda
Conclusions
• Merging sub-stacks of different sensors of the same frequency band but with slightly different characteristics allows continuous monitoring of ground
motions
• The use of cross-interferograms is not possible in our case due to the important relief and the land cover The acquisitions with the appropriate baselines values have a very different incidence angle
• Selecting the acquisitions with similar incidence angles allows the retrieval of the majority distributed-scatterers like pixels determining factor for data selection
• There are three key points within the processing that must be considered in the PSI processing:
• Precise coregistration• The identification of the common coherent scatterers• The calibration rule to produce the Time Series
Perspectives
• Analyzing carefully possible correlations of the slope orientation with the variations of the coherent areas when merging different sub-stacks of interferograms
• Performs adaptive common bandwidth filtering to the cross-interferogram to look for coherent slopes within the swath despite of the spectral shift of more than 1 GHz
Local incidence map
RED – coherence decreases
when adding TSX data to the
CSK stack
GREEN – coherence
increases when adding TSX to
the CSK stack
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T.: +34 93 183 57 50
Javier Duro, ALTAMIRA [email protected]
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