IEEE - Aerospace and Electronic Systems - October 2021 - 5

Credit: Image licensed by Ingram Publishing
geometric relationships between GBSAR traveling distance
to accurately measure the spatial position and small changes
of a certain point on the ground surface. The experiments
conducted proven that GBSAR can even detect millimeters
or submillimeters deformation ofthe earth surface [8].
For small-area monitoring, GBSAR is proven to be
more stable than spaceborne SAR as the linear motion
of the ground-based system is more predictable and stable
compare to the spaceborne system. It can be set up
based on the specific geometric scenes specifically for
the target monitoring area and obtain the deformation
trend and overall deformationcharacteristics of the area
and effectively supplement the spaceborne SAR system
[9]. Compared with spaceborne SAR, ground-based
SAR has the advantages of easy to set up, adjustable
observation angle, and near real-time monitoring capabilities.
Therefore, it has gradually attracted widespread
attention from domestic and foreign experts and scholars
to explore more potential applications especially for
disaster monitoring.
The monitoring of dam displacement by the GBSAR
system shows the application potential of the GBSAR system
in civil engineering [10]. In 2003, Ellegi-LiSALab
obtained a license from the Joint Research Centre of the
European Commission to use Linear SAR (LiSA) technology.
The first commercially developed system was called
the LiSA system, which was later developed as LiSALab
system. The advanced sensors developed afterward have
improved the stability, bandwidth capability, and versatility
of GBSAR. The Image By Interferometry Survey-S/L/
M provided by Ingegneria Dei Sistemi in Italy has demonstrated
a large number of applications via GBSAR technology.
It is currently the most popular commercial
GBSAR sensor. There are other GBSAR systems, such as
the GBSAR system researched by the University of Sheffield
in the United Kingdom, the broadband polarized
GBSAR system researched by the Tohoku University in
Japan, and the ground-based Arc-Scanning SAR system
by South Korea's Research Institute of Geoscience and
Mineral Resources (KIGAM). The FastGBSAR concept
OCTOBER 2021
introduced by MetaSensing increases the fast scanning
time of the GBSAR to several seconds. Faster scanning
has led to a significant improvement in GBSAR's performance
in detecting ground displacement. Besides, the
Remote Sensing Laboratory of the Universitat Politecnica
de Catalunya in Spain, Swiss' Gamma Remote Sensing,
and National Academy of Sciences of Ukraine, Institute
of Radiation Physics and Electronics have also developed
their own GBSAR.
This article presents the GBSAR system design concept,
as well as some indoor and outdoor test results ofthe developed
system. The section " GBSAR Fundamentals " outlines
the background theory of GBSAR, whereas " System
Implementation " describes the hardware implementation.
" Experiment and Results " presents the measurements'
results obtained in the laboratory as well as series ofoutdoor
field test. Last, we present the " Conclusion. "
GBSAR FUNDAMENTAL
Similar to the spaceborne SAR or airborne SAR interferometric
measurement technology, the GBSAR system is used
directly on the land to measure the micro displacement of
the object or the surface of the earth. The basic principle is
to extract the phase information from the radar complex
image to obtain the interference phase [11]. Further signal
processing enables the user to obtain the actual deformation
value. The ground-based differential interferometric measurement
technology in this article mainly uses the three key
technologies, i.e., wideband linear frequency modulation
continuous wave (LFMCW) technology, SARimaging technology,
and differential interferometry measurement technology
to achieve long range, large monitoring range, and
high precision displacement monitoring.
GEOMETRY OF GBSAR SYSTEM
Unlike the spaceborne SAR interferometry technology,
which requires baseline estimation, leveling effect, and
IEEE A&E SYSTEMS MAGAZINE
5
IEEE - Aerospace and Electronic Systems - October 2021

Table of Contents for the Digital Edition of IEEE - Aerospace and Electronic Systems - October 2021
