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URBAN MONITORING USING PERSISTENT SCATTERER INSAR AND
PHOTOGRAMMETRY
Junghum Yu*, Alex Hay-Man Ng, Sungheuk Jung, Linlin Ge, and Chris Rizos.
School of Surveying and Spatial Information Systems, University of New South Wales, Australia.
jung.yu@student.unsw.edu.au
KEY WORDS: Persistent Scatterer, InSAR, Urban Monitoring
ABSTRACT:
The purpose of this paper is to monitor deformation due to groundwater extraction in urban area using Persistent Scatterer InSAR
(PSInSAR) and Photogrammetry. Theoretically, PSInSAR technique allows for millimetre precision ground deformation mapping
based on the utilization of long period of interferometric SAR data. One main advantage of PSInSAR method, compared to
conventional deformation surveying methods such as levelling and Global Positioning System (GPS), is the coverage of large area.
However, PSInSAR method has difficulty in explanation of each single object or detail information of small objects because of
current space-bome radar imagery which has approximately 25m spatial resolution. In order to solve this problem, we used aerial
photogrammetry method to survey detail information of objects in selected area identified by PSInSAR.
1. INTRODUCTION
Nowadays, continuous monitoring of urban area represents one
of the most interesting and major subjects of research in remote
sensing whenever a Synthetic Aperture Radar (SAR) instrument
is used. Typically, the aerial photogrammetry and Light
Detection and Ranging (LiDAR) methods which have high
spatial resolution were used for urban monitoring. Major cities
have rapidly changed and extended during last century and over
50 percentage of the population now live in towns and cities.
Much population who lives exists in the city consuming huge
amount of water everyday. Water supply is main element of city
life maintaining. Surface water and groundwater are two major
water sources in Australia. Water shortage is one of the major
social and economic environmental problems in Australia.
Australia is the driest inhabited continent on Earth, with highly
variable rainfall patterns. The amount of water usage has
increased dramatically in Australia which leads to significant
increase in demand for groundwater resources due to the limit
amount of surface water supplies available. Normally, there are
two surveying methods used for ground deformation monitoring
which include the Levelling and Global Positioning System.
However, it is very difficult to cover the large area and set up
bench marks for the ground survey. Therefore, Persistent
Scatterer Radar Interferometry is used as a complementary
method to conventional surveying method. Theoretically, the
Differential Interferometry Radar (DInSAR) has the potential to
precisely observe the ground deformation along the Line-of-
Sight (LOS) direction up to a few millimetres. However, there
are four main problems, including (1) atmospheric disturbances
causing noise from signal delays, (2) temporal decorrelation of
surface scatterers due to seasonal vegetation and/or other
surface change, (3) geometrical decorrelation due to large
baseline between two images acquisition result in incoherence
and (4) ambiguity, have limited this technique to achieve its full
operational capability. PSInSAR technique allows for
millimetre precision ground deformation mapping based on the
utilization of long time series of interferometric SAR data and
huge area covering. However, current space-bome radar
imagery which have approximately 25m spatial resolution are
difficult to support the PSInSAR for detection of each building
or detail information of small objects [Ge et al, 2001; National
land, 2000; Ng et al. 2007].
2. PERSISTENT SCATTER TECHNIQUE
Space-bome radar interferometry has already proven its
potential for ground deformation monitoring application, for
example, mining, earthquake and volcano studies, due to its
high precision and spatial resolution [Colesanti et al, 2003].
Theoretically, the space-bome radar interferometry has the
potential to precisely observe the ground displacement along the
LOS direction up to a few millimeters. There are four main
problems stated in previous section limited the conventional
DInSAR technique from achieving its full operational capability.
There four main problems are (1) atmospheric disturbances, (2)
temporal decorrelation, (3) geometrical decorrelation, and (4)
ambiguity problems. In the conventional DInSAR process, these
problems may not be identifiable in the interferograms which
have many noises. In PSInSAR process, however, the elevation
and linear velocity rate corresponding to these problems can be
estimated, as well as the atmospheric disturbances [Ferretti et al.
2000, 2001]. The PSInSAR method first identifies all the PS
points and a 2D deformation analysis is then applied to these
points. Millimeter deformations can be achieved with this
method which is more precise than the conventional method.
The Persistent Scatterer (PS) technique is recent development in
radar interferometric processing, which offers a practical way to
reduce the main errors in conventional DInSAR processing
method; temporal and geometrical decorrelation, and
atmospheric artefacts. Atmospheric phase contributions are
spatially correlated within a single SAR scene, but tend to be
uncorrelated on time scales of days to weeks. Thus, atmospheric
effects can be estimated and removed by combining data from
long time series of SAR images, averaging out the temporal
fluctuations. Radar scatterers that are affected by temporal and
geometrical decorrelation are used, allowing exploitation of all
available images regardless of imaging geometry. In a radar
image, the reflected wave from a resolution element is the
coherent sum of individual wavelets scattered by many discrete
scatterers. Positive and negative interference of these waves
takes increase to variation in the phase and amplitude of the
