IEEE Geoscience and Remote Sensing Magazine - June 2020 - 122

TABLE 4. THE SENTINEL-1A DATA USED IN THIS APPLICATION
CASE STUDY.
DATA ACQUIRED

OBSERVATION
MODE

POLARIZATION

PRODUCT
TYPE

2 June 2015

SLC

14 June 2015

SLC

26 June 2015

SLC

20 July 2015

SLC

1 August 2015

SLC

25 August 2015

SLC

6 September 2015

SLC

10 December 2015

SLC

17 November 2015

SLC

29 November 2015

SLC

23 December 2015

SLC

16 January 2016

SLC

28 January 2016

SLC

9 February 2016

SLC

4 March 2016

SLC

16 March 2016

SLC

28 March 2016

SLC

9 April 2016

SLC

21 April 2016

SLC

3 May 2016

SLC

27 May 2016

SLC

7 August 2016

SLC

19 August 2016

SLC

12 September 2016

SLC

resulting in the surface object having less interference on
the deformation monitoring.
There are also some requirements for the image quality
of SAR data. Good raw data quality is the basis for obtaining high-coherence interferograms. First, the interferometric mode and data range of
IN CONTRAST TO PSInSAR,
SAR images should be consisSBAS PAYS MORE
tent, including polarization,
ATTENTION TO DISTRIBUTED
incidence angle, and so on.
TARGETS, MAKING IT THE
Second, the original SAR data
FIRST SUCCESSFUL
should comprise single look
APPLICATION OF TIME
complex (SLC) images. For
SERIES InSAR TECHNOLOGY
the data of adjacent tracks, it
IN NONURBAN AREAS.
must be ensured that the data
overlap rate is greater than or
equal to 10%. The selection
of general SAR data is based on the specific monitoring
tasks and characteristics of the monitoring area.
Sentinel-1A data are widely used due to their moderate
resolution and wavelength, and they are suitable for the
deformation monitoring of most surface conditions. At
the end of 2005, the European Commission decided to
122

implement the Copernicus Plan, and Sentinel-1 was the
first satellite designed specifically for the Copernicus Plan
to monitor the environmental changes of the land and sea
surfaces in Europe, Canada, and the polar region. The Sentinel-1 satellite is a C-band radar imaging system that enables
the high-resolution imaging of terrestrial and coastal areas
around the world. Sentinel-1 radar image data have the advantages of a short repeat cycle, good current situation,
and extensive image coverage. The repeat cycle of the dual
constellation can be shortened to six days. The Sentinel-1
radar satellite has a variety of observation modes, such as
extra-wide swath, stripmap mode, interferometric wide
swath (IW), and wave mode. Its default mode over land
is the IW mode, in which the swath width is 250 km. The
Sentinel-1 radar satellite produces a higher-quality, more
uniform image that greatly enhances the imaging radiation performance. For geoscience research, these data have
unique advantages.
The study data in this article used 24 Sentinel-1A images
for the period from 2015 to 2016. Table 4 shows detailed
image data information. The DEM data used in this study
were a high-precision DEM of 30-m ground resolution produced by the Japan Aerospace Exploration Agency and Remote Sensing Technology Center of Japan using optical images, namely, AW3D30 data. The precision orbit parameter
file was AUX_POEORB.
DATA PROCESSING CHAIN AND KEY TECHNOLOGY
DATA PREPROCESSING
In the early stage of SBAS processing, it is necessary to
prepare SAR images suitable for the characteristics of the
monitoring area, DEM data, precise orbit parameter files,
and data processing equipment. It should be noted that
the data range of a prepared DEM is generally larger than
the image coverage of SAR data. According to the needs of
deformation monitoring in oil and gas production areas,
Sentinel-1A images are cropped using the vector file of the
region of interest. Generally, the range of a cropped SAR
image should be equal to or greater than that of the monitoring area. Otherwise, the cropping operation needs to
be performed again. After the cropping, the intensity map
needs to be checked in detail to see if the actual cropping
area covers the region of interest and has the same range.
Otherwise, the interferogram cannot be generated in subsequent operations. The preprocessed SAR data are stored in a
designated folder for later InSAR processing.
CONNECTION OF SB INTERFERENCE PAIRS
After the data are preprocessed, the critical baseline threshold
is set according to the principle of SB combination, and the
temporal baselines and SBs of all SAR images are analyzed.
The interference image pairs whose temporal baselines and
SBs are smaller than a given threshold are selected to form the
baseline connection diagram of the interference image pair.
It should be noted that the selection of the critical baseline
IEEE GEOSCIENCE AND REMOTE SENSING MAGAZINE

JUNE 2020

IEEE Geoscience and Remote Sensing Magazine - June 2020

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