GB-SAR for Landslide monitoring
GB-SAR is a fixed radar device that uses radio waves
to measure ground surface displacements up toseveral kilometers away with an accuracy of 1 mm.
Advantages over conventional methods.
• No need to estimate danger zones and installsensors• All positions can be measured with one device• Not affected by weather

At 8:43 on June 14, 2008, an earthquake
measuring 7.2 on the Richter scale and measuring
a maximum seismic intensity of 6+ occurred ininland Iwate Prefecture. This was the IwateMiyagi inland earthquake. Landslides occurred in
3,500 locations, large and small.

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The Arato-zawa landslide was the largest of its
kind in Japan. The Motoyuki Sato Laboratory at
Tohoku University has been monitoring the site.
The landslide began between the Niseko River andthe Misase River, which flow out of the Aratozawa Dam, and continued along a 1,300-meterslope.
Monitoring the Arato-zawa landslide site wasmade possible by the development of the"Ground-Mounted Synthetic Aperture Radar (GBSAR)." GB-SAR, which can survey a wide area bymoving the radar body. This monitoring method
can confirm the ground surface displacement is asa 3D image. This is made possible by "uniqueradar analysis technology." Data observed by GBSAR is merely a waveform graph, but it isautomatically processed by a dedicated computerat Tohoku University to create a highly accurate
3D diagram of ground surface displacement. Since
2023, ALISys Co., Ltd. is continuing this monitoring.

MIMO GB-SAR
Conventional GB-SAR must acquire data with anaperture width of 2m at 5mm intervals whilemoving the antenna. The Nyquist constraintrequires an interval of less than half a wavelength.
In order to obtain the same data as GB-SAR at
Arato-zawa, by arranging many antennas while
suppressing the occurrence of false images, 200
antennas are required, making the device complex.
MIMO (Multiple-Input Multiple-Output) type GBSAR is a technology that prevents the occurrence offalse images while significantly reducing thenumber of antenna elements by sparsely arranging
transmitting and receiving antennas.
MIMO type GB-SAR can measure vibrations of a few
Hz with a repetition frequency of 10 Hz or more.
ALISys completed a 79 GHz band commercial
MIMO GB=SAR product in 2024.

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Projected image of integrated 3D image on
optical image

MIMO GB-SAR operates at the frequency of79 GHz and achieves maximum measurement
range over 100m and cm-order resolution
MIMO GB-SAR consists of stereo camera andradar circuit with radome
This radar has 24 transmitting (Tx) antennas
and 32 receiving (Rx) antennas, 8 radar ICs
and 8 onboard computers
Stereo camera captures optical images by
each sensor on right and left side, derives
parallax information and composes 3D point
cloud data

In addition to generating 2D SAR images andperforming interferometric SAR analysis, theMIMO GB-SAR can measure vibrations at specificpositions in the images.