Application of D-Insar Technique on Ground Movement Monitoring

8/2/2019 Application of D-Insar Technique on Ground Movement Monitoring

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APPLICATION OF D-INSAR TECHNIQUE ON GROUND MOVEMENT MONITORING

Guijie WANG, Mowen XIE, Jiehui HUANG, Weilun WU

University of Science and Technology Beijing, Beijing, CHINA, 100083

KEY WORDS: D-INSAR, Landslide, Subsidence, Monitoring,Ground Movement

ABSTRACT: Differential Synthetic Aperture Radar interferometry (D-INSAR), which allows to analysis very small

ground movement and to cover in continuity large areas, has turned out to be a very useful technique for the

measurement of ground movement. D-INSAR technique has been widely used for geological hazard investigating on

subsidence, landslide, earthquake and volcanic activity. In this paper, Three-Pass method of D-INSAR techniques

has been used to monitor the ground movement of a landslide area of certain hydropower and the subsidence of

Heyuan city of Guangdong province. Three SAR acquisitions (C-band, VV-polarized) of a landslides area are

acquired from ASAR Sensor of ENVISAT satellite (2004.06.07- 2005.03.14), the derived result illustrates the

position, the variation ground movement and the detailed deformation map. Three SAR acquisitions (L-band,

HH-polarized) of Heyuan subsidence area are acquired from PALSAR Sensor of ALOS satellite (2007.02.18-

2008.02.21), the analytic result shows the vivid subsidence condition .It also indicates that the deformation is littlish

in urban district comparing with in other district. The analysis and comparison of the two examples of theexperimental data show that the D-INSAR technology is a possible solution for landslides movement monitoring and

subsidence investigating.

1. INTRODUCTION

Ground movement causes various geological hazards (e.g. subsidence, landslide, earthquake, volcanic activity) has

become a global concerned problem. However, the conventional geodetic technique is highly incompetent for the

large-scale and serious land deformation monitoring (Yao and Mu, 2008). With the development of remote sensing,

Differential Synthetic Aperture Radar interferometry (D-INSAR) technique has exactly latent ability to solve this

problem, which allows to monitor very small movements of the ground and to cover in continuity large areas in

principle. Accordingly, it has been widely applied on geological hazard investigating for scientific research and risk

assessment and monitoring (Gabriel et al., 1989; Massonnet et al., 1993, 1995; Goldstein et al., 1994; Achache et al.,1995; Carnec et al., 1996; Amelung et al., 1999; Kimura and Yamaguchi, 2000; Paolo et al., 2003; Colesanti and

Wasowski., 2006; Samsonov et al., 2008; Fernandez et al., 2009).

In this paper we focuses on the description and analysis of the results which use Three-Pass D-INSAR technique to

monitor the ground movement of a landslide area of near Wudongde hydropower and the subsidence of Heyuan city

of Guangdong province. The analytic result of the landslide area illustrates the detailed displacement value and the

deformation map of surrounding region. The subsidence result shows the vivid subsidence condition and detailed

displacement of the city region and it also indicates that the deformation is littlish in urban district comparing with in

other district. The analysis and comparison of the two examples show that the D-INSAR technology is a possible

solution for landslides movement monitoring and subsidence investigating in practice.

2. THE RATIONALE OF D-INSAR AND THE PROCESS OF OBTAINED DEFORMATION

2.1The Rationale of D-INSAR

The phase difference of two complex interferometric SAR images is related to the same scene topography and to

ground deformation, which one complex interferometric SAR image contain, only topographic phase term and the

other complex interferometric SAR image contain, both topographic phase term and deformable phase term. The

topographic phase term can be easily eliminated if orbit data and topographic information (for instance, a known

Digital Elevation Map, DEM) are available. The remaining phase term is proportional to the ground deformation

(projected along the SAR line of sight). The accuracy of the measurement is of the order of fractions of the employed

electromagnetic wavelength: accordingly, at microwave frequencies, the accuracy can be of the order of fractions of a

centimeter (Paolo et al., 2003). The complex interferometric SAR image is constructed by two Single-Look Complex

(SLC) images taking precise registration and interferometry processing and the single-Look Complex (SLC) images

is derived from before-and-after deformation.

Conventional D-INSAR technology, including Two-Pass method, Three-Pass method, and Four-Pass method. Their


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geometric principle is homologous basically .In this paper, Three-Pass method is used for analysis. The geometrical

sketch of D-INSAR of three-pass will be shown as followsFig.1 (Wang et al., 2009):

dR

1 2

B//

B

1

2

3

1r

2r 3r

21

Fig.1 The Geometrical Sketch of D-INSAR of Three-Pass.

InFig.1,1A , 2A , 3A is the positions of three times imaging by the satellite. According to the geometrical relation in

Fig. 1 and211 rrB +


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Fig.2 Flow Chart of D-INSAR Data Processing.

3. APPLICATION OF D-INSAR ON THE STUDY AREAS

3.1 Application on a Landslide area of Near Wudongde Hydropower

The landslide area near Wudongde Hydropower which is located in Jinshajiang river basin (Fig.3a).

Fig.3aThe Study Area of Near Wudongde and Fig.3b The Study Area of Heyuan City.

In our experiment, 3 ENVISAT acquisitions have been obtained, the wavelength of which is 0.0562356 m, spanning

a time period of 9 months from June 2004 to March 2005(Table 1).

Table 1The ENVISAT Data Processing Parameters of D-INSAR on the Landslides.

Image

pair

Satellite sensor Acquisition number Obtained

date

Ascending orbit/

Descending orbit

Time span

(day)

Perpendicular

baseline (m)

ENVISAT ASAR ASA_IM_0CNPDE20040607 2004-06-07 DescendingAT

ENVISAT ASAR ASA_IM_0CNPDE20041025 2004-10-25 Descending

140 153.14

ENVISAT ASAR ASA_IM_0CNPDE20040607 2004-06-07 DescendingAD

ENVISAT ASAR ASA_IM_0CNPDE20050314 2005-03-14 Descending

280 212.772

The image with the time on June 7th 2004 has been selected as the master image. The image pair with the time on June

7th2004 and the time on October 25th 2004 has been selected as the topographic image pair AT which contain only

topographic phase term. The image pair with the time on June 7th 2004 and the time on March 14th 2005 has been

selected as the deformable image pair AD which contains both topographic phase term and deformable phase term.

The STRM3 DEM is used as auxiliary DEM in data processing.

After the raw data focused, the number of the image samples is 5168, and the number of the lines is 24,376. Through

precision registration and interferometry processing, 2 interferograms(AT, AD)are generated (Fig.4a).

SLC2 SLC1 SLC3Baseline Estimation

Interferogram1

multilooking Coregistration multilooking

Flattening and Filter

Interferogram2

Flattening and Filter Coherence Map

Phase UnwrappingPhase Unwrapping

Phase Editing

Baseline Fit

Phase Difference

Geocoding

Baseline Fit

Displacement Map

Coregistration

a b


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Fig.4a Interferogram Originally and Fig.4b Interferogram after Flattening and Filte.

For eliminating the phase of the earth ellipsoid surface and phase noise, flattening and filter must be carried out

(Fig.4b). And Coherence Map (Fig.5) is generated too.

Fig.5The Coherence Map of the Two Inteferometric Image Pair.

At last, through Phase Unwrapping, Phase Difference and Geocoding obtain the DEM and displacement map which

contain detailed displacement information of the study area (Fig.6a and b).

Fig.6a The DEM Map of Landslide Area and Fig.6b the Vertical Displacement Map of Landslide Area.

3.2 Application on the Subsidence of Heyuan City

Heyuan city is located in Guangdong province, China (Fig.3b). In our experiment, 3 PALSAR acquisitions have been

obtained, the waveband of which is L-band, spanning a time period of 1 year from February 2007 to February

2008(Table.2). The image with the time on January 6th 2008 has been selected as master image. The image pair with

the time on January 6th 2008 and the time on February 18th 2007 has been selected as the topographic image pair BT

which contain only topographic phase term. The image pair with the time on January 6th 2008 and the time on

February 21th 2008 has been selected as the deformable image pair BD which contains both topographic phase term

and deformable phase term. The STRM3 DEM is used as auxiliary DEM in data processing.Table 2 The PALSAR Data Processing Parameters of D-INSAR on the Subsidence

Image pair

number

Satellite

sensor

Acquisition number Obtained

date

Ascending orbit/

Descending orbit

Time span

(day)

Perpendicular

baseline (m)

ALOS PALSAR ALPSRP056970460 2007-2-18 AscendingBD

ALOS PALSAR ALPSRP103940460 2008-1-6 Ascending

322 964

ALOS PALSAR ALPSRP103940460 2008-1-6 Ascending

BT ALOS PALSAR ALPSRP110650460 2008-2-21 Ascending

46 607

After the raw data is focused, the number of the image samples is 9344, and the number of the lines is 18,432. On the

basis of section 3.1, in this subsection through D-INSAR processing obtained the subsidence results of Heyuan city as

follows (Fig.7)

AT(20040607and20041025) AD(20040607and20050314)bAT (20040607and20041025) AD(20040607and 20050314)a

(a)

(b)

AT(20040607and20041025 AD(20040607and20050314


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Fig.7a Interferogram Originally and Fig.7bInterferogram after Flattening and Filter.

Fig.7cThe Coherence Map of the Two Inteferometric Image Pair.

Fig.7d The Vertical Displacement Map of the Subsidence.

4. RESULTS AND DISCUSSIONS

4.1 Results of the Landslides Area and Their Interpretation

The rough results and the processing procedures are described in section 3.1. From interferential fringe is not

very clear-cut in the obtained interforegrams, we know that the 3 ENVISAT acquisitions is not perfect. The reasons

perhaps have the two aspects besides the imperfection of D-INSAR technique in itself. First, the 140 days

time-baseline is too long for topographic image pair AT, where smaller is better for time-baseline in principle and a

repeat cycle 35 days is better for ENVISAT satellite. Secondly, the launched time is longer on March 2002 for

ENVISAT satellite. Therefore, we use a small segment of the exaggerated image to improve clarity (Fig.4a,b).

To describe the deformation of certain landslide in detail, we get the vertical Map of Jinpingzi landslide area

(Fig.8a) and Dashicheng landslide area (Fig.8b) from the whole deformation Map (Fig.6b).

Fig.8a Jinpingzi Landslide Vertical Map and Fig.8b Dashicheng Landslide Vertical Map.

From the results of some typical point movement, it is clear that the maximum displacement is -4.7651cm and the

BT(20080106and200802 BD(20080106and200702(b)BD (20080106and20070218)BT (20080106and20080221) (a)

-1.7875cm-7.5225cm

-5.971cm

-4.5863cm

-4.4594cm

-4.7651cm

-4.5138cm

-7.0699cm

-5.8964cm-5.8373cm

-5.7993cm

-5.8752cm-5.8734cm

-7.9721cm

-5.8354cm

-6.4624cm-6.3993cm

-6.4430cm

-8.5928cm-8.7867cm

-9.5129cm-9.9172cm

-7.5289cm

-7.3099cm

-7.5104cm-7.4505cm

-7.4763cm-7.5602cm

-6.4607cm

BT(20080106and20080221) BD (20080106and20070218)


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minimum displacement is -4.4594cm in Jipingzi landslide area, and the displacement of certain point is up to

-7.5225cm around the landslide area. In Dashicheng landslide area, the many typical point movement can be derived,

its maximum value is -9.5129cm and minimum value is -5.7993cm.

4.2 The Subsidence Results and Their Interpretation

The results and the processing procedures are described in section 3.2. The inteferogram (Fig.7a, b) and theCoherence Map (Fig.7c) are more vivid, it can be concluded that the 3 PALSAR data is fit for this subsidence

processing. Also based on the subsidence Map (Fig.7d), it is known that the urban subsidence is not very obvious

comparing with in other district and its maximum subsidence value is -3.215cm in the time period of 1 year from

February 2007 to February 2008.

5. CONCLUSIONS

In this paper, the use of the D-INSAR technique on the landslides area and subsidence has been explored. From

obtained detailed deformation map, the tendency and the state of the landslide area and subsidence can be obtained,

this will become an important method for detecting and preventing against the landslide disaster and subsidence. It is

known that, D-INSAR technique has some well-know limitation of the decorrelation noise and the difficult Phase

Unwrapping, especial for landslide area. To overcome these problems, some promising methods have been developed

based on the integrate D-INSAR technique of Permanent Scatters PS and Global Positioning System GPS. Theanalysis and comparison of the two examples of the experimental data show that the D-INSAR technology is a

possible solution for landslides area monitoring and subsidence investigating. It is confirmed that D-INSAR

technique is a feasible and effective method for monitoring ground movement.

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Application of D-Insar Technique on Ground Movement Monitoring

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