Peer-Reviewed Articles
1131 A Quantitative Measure for the Quality of InSAR Interferogram
Based on Phase Differences
Zhilin Li, Weibao Zou, Xiaoli Ding, Yongqi Chen, and Guoxiang Liu
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It is well-known that interferometric SAR (INSAR) is a technology
for the generation of high-precision digital elevation
models (DEM) and the precise measurement of terrain surface
deformation. The accuracy of DEM and deformation measurement
is highly dependent on the quality of the interferogram
generated. Such an interferogram is constructed by a pointwise
complex multiplication of corresponding pixels in both
datasets, which are respectively contained in master image
and registered image.
An exanimation of existing literature reveals that there is no, good, quantitative measure for the quality of interferograms, and visual inspection is still the best solutions available so far. By visual inspection, one recognizes those interferograms with continuous fringes as good ones and regards those with many discontinuous interferograms and speckles as being not good. As the pixels in the interferogram represent the phase value values, it is natural to think that, if the quality is good, the phase differences between neighbor pixels should be small, and thus the sum of all phase differences will still be small. This leads to the proposal of “sum of phase differences” (SPD) as a quantitative measure for the quality of interferogram. Two simulation tests have been conducted, and the results show that the SPD is a reliable measure.
1139 Automatic Registration of InSAR Data Based on Least-Square Matching
and Multi-Step Strategy
Mingsheng Liao, Hui Lin, and Zuxun Zhang
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Interferometric Synthetic Aperture Radar (INSAR) allows for
production of high resolution DEM and detection of small earth
deformation using multiple-pass SAR data sets. The automatic
algorithm for registration of the INSAR data is one of the key
points for improving both accuracy and efficiency. In this
paper, an automatic approach based on multi-step matching
strategy is presented and only intensity components of SLC images
are involved in relevant computation. Both probability relaxation
and Least-Square Matching (LSM) algorithms have
been introduced to maintain reliability and improve accuracy.
All the procedures could be automatically implemented. Primary
results are promising and reveal the potential for operational
INSAR data processing.
1145 Application of SAR Interferometry on DEM Generation of the Grove
Mountains
Dongchen E., Chunxia1 Zhou, and Mingsheng Liao
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The Grove Mountains Area is situated to the southwest of
Princess Elizabeth Land, the inland areas of east Antarctica.
Adopting Landsat-4 TM images, a coloured satellite image
map of Grove Mountains was produced and used to design an
expedition route to Grove Mountains in 1998. In 2000, a field
survey of the core area was completed with GPS and total station
surveys. However, traditional mapping methods are no
longer the most efficient means of obtaining topographic
maps or DEM in large areas, especially those areas that are
more inaccessible. Synthetic aperture radar interferometry
has been proposed as a potential technique for digital elevation
model (DEM) generation, topographic mapping, and surface
motion detection. This paper presents an experimental
investigation of the ERS-1/2 SAR tandem data on DEM generation
of the Grove Mountains Core Area, and compares the DEM
derived by INSAR with the DEM generated using field survey
data. The paper confirms that INSAR is a very valuable technique
to be utilized in Antarctica, and that INSAR can be employed
to produce complementary field survey products.
1151 Ground Subsidence Monitoring in Hong Kong with Satellite SAR
Interferometry
X.L. Ding, G.X. Liu, Z.W. Li, Z.L. Li, and Y.Q. Chen
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Ground settlement has long been a problem in Hong Kong, as
most usable land in Hong Kong was reclaimed from the sea.
Ground settlement may affect building structures and underground
facilities such as water supply and sewage systems
built on the land. Measurements of ground settlement can
provide valuable data for assessing the impacts of ground settlement
and for improving designs of future land reclamation
projects.
Experiments have been carried out to assess the performance of INSAR in the environment of Hong Kong especially the temporal decorrelations of SAR images and the potential atmospheric effects on INSAR measurements, and to use INSAR to study the ground settlement problem in Hong Kong. This study finds that the temporal decorrelation is an important problem in the heavily vegetated rugged areas as usually expected, and that the atmospheric effects can be very significant at times. Ground settlements measured over the airport and a residential area are presented. It can be seen from the results that both of the areas are still settling significantly many years after the reclamation.
1157 Applying SAR Interferometry for Ground Deformation Detection
in China
Chao Wang, Hong Zhang, Xinjian Shan, Jin Ma, Zhi Liu, Suozhonh
Cheng, Guonian Lu, Yixian Tang, and Ziqi Guo
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This paper applies SAR Interferometry for ground deformation
in two cases: the 1998 Zhangbei-Shangyi Earthquake in
Northern China and the urban subsidence in Suzhou City
from 1993 to 2000. It is concluded that SAR interferometry
may provide valuable information for understanding the
spatial patterns and progress of natural hazards. SAR interferometry
is also critical for mechanism studies and hazard
mitigation.
1167 Landslide Monitoring in the Three Gorges Area Using D-INSAR and
Corner Reflectors
Y. Xia, H. Kaufmann, and X.F. Guo
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The differential INSAR technique has the potential for monitoring
centimeter-scale ground motion in an accurate and costeffective
manner. Probably the most important limiting factor
in the application of INSAR is temporal change in the complex
reflectivity of the ground surface during the period between
radar acquisitions. This can be due to changes in such parameters
as moisture content or vegetation. The stable artificial
corner reflectors can be identified from long temporal series
of interferometric SAR images even with large baselines, and
therefore decrease the risk of image decorrelation. This paper
will discuss the following questions: 1) how to obtain the true
phase of a corner reflector in a SAR complex image; 2) how to
co-register the corner reflector pixels when the coherence of
its surrounding area is extremely low; 3) how to select the interpolation
kernel to resample the SAR image; and, 4) how to
compute the interferometric phase of two co-registered corner
reflectors without flat earth term and corners’ height contribution.
In order to demonstrate the results, a practical example
of landslide monitoring in the Three Gorges area in China is
presented.
1173 GPS and GIS Assisted Radar Interferometry
Linlin Ge, Xiaojing Li, Chris Rizos, and Makoto Omura
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Error in radar satellite orbit determination is a common problem
in radar interferometry (INSAR). For example, when we try
to locate a radar test site with known geographic coordinates
using the geocoding information in SLC (the latitude and longitude
of the four image corners), the location is well away from
the true position. Another example is when there is a significant disturbance
in the differential INSAR result, we sometimes
are not sure whether it is from ground deformation or atmospheric
heterogeneity. Even after these are corrected, we need
to export the INSAR results to a GIS format so that they can be
overlaid as layers over orthophotos and mine plans (in the
case of mining subsidence) in order to interpret the results.
Therefore, it is proposed to use both GPS and GIS to assist radar
interferometry. Results are presented with an application to
monitoring subsidence due to underground mining southwest
of Sydney, Australia.
1179 Detection of Rapid Erosion in SE SPAIN: A GIS Approach Based
on ERS SAR Coherence Imagery
Jian Guo Liu, Philippa Mason, Fiona Hilton and Hoonyol Lee
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This paper presents an integrated remote sensing—GIS approach
for identifying areas vulnerable to rapid erosion in
Almería Province, Southeast Spain. Earth Resources Satellite
(ERS) Synthetic Aperture Radar (SAR) multi-temporal interferometric
coherence imagery has been used to detect rapid erosion
that causes random changes in the micro-topography of
a land surface. These small scale changes result in reduced
coherence of the radar signals between the initial and eroded
states. However, the detection solely based on coherence imagery
is not exclusive because other factors may cause losing
coherence as well. A Geographic Information System (GIS) is
then used to derive criteria for a set of environmental conditions
favourable to rapid erosion from multi-datasets including
Landsat Enhanced Thematic Mapper (ETM) imagery and
geological maps. The areas predicted to be most vulnerable to
rapid erosion across the imagery are then identified where
hard evidence of low coherence coincides with favourable
conditions.
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