landslide monitoring in three gorges area by joint use of phase...
TRANSCRIPT
Landslide Monitoring in Three Gorges Area By Joint Use of Phase Based and Amplitude Based Methods
Xuguo Shi , Lu Zhang, Mingsheng Liao, Timo Balz
LIESMARS, Wuhan University
Outlines
• Introduction
• InSAR Results
• Pixel Offset Tracking Results
• Summary
Part 1: Introduction
Test Site: Three Gorges area (Began to function in 2003)
2003 20052004 2006 2007 2008 2009 2010
Dam
66m
135m
156m
185m
175mReservoir impoundment events along
with dam construction/operation
Geohazards in the Three Gorges area
dominant 67% of total
Adapted from Liu et al., 2009
Difficulties for landslide monitoring in TG
Steep terrain
Dense vegetation cover
Complicated atmospheric condition
Part 2: Datasets and InSAR Results
TerraSAR-X datasets
HS: High resolution Spotlight SM: StripMap
Basic parameters
SM data HS data
Orbit direction Descending Descending
Heading 190.7 189.6
Look angle(°) 24 39
Polarization VV HH
Azimuth spacing(m) 1.96 0.87
Range spacing(m) 0.91 0.45
Temporal Coverage Jul 2008-May 2010 Jan 2009-Apr 2010
Az
Rg
N
Fanjiaping Shuping
Qianjiangping
Kaziwan
Xintan
Lianziya
Locations of major landslides
Mean amplitude of 34 TerrraSAR-X StripMap images
What can InSAR do in landslide monitoring ?
What can InSAR observe?
InSAR is useful for monitoring slow moving landslides!
TerraSAR-X Interferogram (SM mode)
Kaziwan
Fanjiaping Shuping
Qianjiangping
Az
Rg
N
Wangjiawan
Xintan
Lianziya
(20091128 -20091220, Bp=13 m, Bt=22 days)
Fanjiaping landslide motion detected by SBAS
The southern part of Fanjiaping landslide is very active.
Deformation rate can reach 5cm/y.
Time series deformation indicated Fanjiaping was moving during the
whole period.
Part 2: Pixel offset tracking results
1000
Fast moving landslides in Three Gorges
Miao et al., Eng. Geology, 2014
Underestimation on these landslides will happen with InSAR analyses.
How to catch the deformation of the fast-moving landslides using high-
resolution SAR images ?
InSAR Point-like targets offset tracking
Shuping Landslide (PS-InSAR)
Active deformation observed in differential interferogram.
Deformation rate estimated by PS-InSAR was unreasonably
less than 1 cm/year.
Underestimation happened with sparse PS points identified.
Shuping landslide is a south-north oriented slope.
Point-like Targets - Corner Reflectors
14 CRs were identified on Shuping landslide.
4 CRs were installed outside Shuping landslide.
Point-like targets offset tracking (PTOT)
– Based on SAR image matching at subpixel-level accuracy
– Make use of pixels with high amplitude values
– Avoid noisy measurements in vegetated areas
– Without phase unwrapping
– Can measure displacements at centimeter-level accuracy in both line-of-sight direction (LOS) and azimuth directions
* LOS ≈ vertical and east-west directions
* Azimuth ≈ north-south direction
Suitable for measuring large displacements.
=>>> Hu, Wang &Liao, IEEE GRSL, 2014 Wang & Jonsson, IEEE JSTARS, In Press
Workflow of PTOT
PT Detection
Time Series
SAR Images
Master Selection
Co-register
Mean Amplitude Sinc Function
PT Candidates
Offset Tracking
Amplitude Correlation and
PT Reselection
Cull PointsCommon
PTs
Orbital Ramp Estimation
Pixel Offset Extraction from
Slave Images
Time Series
Deformation
-
– Mean amplitude image were used to select PT candidates.
– Common PTs were used in the final time series analysis.
Displacement at Shuping measured by HS data (20090221-20100415)
The displacement in azimuth
and range directions can
reach more than 0.8 meters
and 0.6 meters respectively.
Azimuth (m)
Range (m)
InSAR measurement
significantly underestimated
deformations in the LOS
direction.
Displacement at Shuping measured by SM data (20080721-20100501)
The displacements in azimuth
and range direction can reach
more than 1 meter and 0.8
meters respectively.
Observations coincide with the
conclusions in Wang et al. 2008
that the eastern part of Shuping
landslide is more active.
Moving towards north direction
into the Yangtze River.
Azimuth (m)
Range (m)
Time series analysis
Azimuth
Range
Water level
decline VS
displacement ?
Good agreement
achieved on
CR14 between
HS and SM.
BUT ?
Comparison between HS and SM
CR6-Azimuth Range
CR15-Azimuth Range
Projection
sin sin cos sin cos
cos sin
rg rgN E V
az azN E
D D D d
D D d
DN, DE, DV :displacements in the northing, easting and vertical
directions.
α and θ : heading angle and nominal incidence angle at the target
point.
drg and daz : displacements measured in range and azimuth.
δrg and δaz : observation errors to be minimized.
Is it possible to combine HS and SM measurements ?
AX B
sin sin cos sin cos
cos sin 0
sin sin cos sin cos
cos sin 0
HS HS HS HS HS
HS HS
SM SM SM SM SM
SM SM
A
T
N E VX D D D
THS HS SM SMrg az rg azB d d d d
1( )ˆ T TA AX A B
Typical Design matrix
0.115 0.679 0.725
0.986 0.167 0
0.083 0.436 0.896
0.982 0.187 0
A
North East Vertical
HS SM
Rang measurements by HS data is more sensitive to displacement in
easting direction than that by SM data while the latter is more
sensitive to vertical displacement.
Three dimensional displacement (200902-201004)
Horizontal
Vertical
• InSAR and pixel offset method could be jointly used to more accurately map the landslides in TG.
• It is possible to derive 3D displacement from two descending orbit with different look angles.
Summary