NEC Technology Reliably Measures Sea Levels from a Greater Distance

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NEC Corporation has developed a technology for measuring sea levels with high accuracy from greater distances using 3D Light Detection And Ranging (LiDAR), a remote sensing technology. This technology makes it possible to reliably measure sea levels, even in the event of a tsunami or ground movement at the location where the measuring equipment is installed. In June 2024, NEC conducted a demonstration test of this technology in Tokyo Bay and confirmed that it can measure sea levels with high accuracy from a greater distance than conventional technologies.

Background

In the event of a tsunami caused by an earthquake, volcanic eruption, or other phenomenon, immediate and accurate assessment of changes in sea levels is critical to saving lives. Current radio wave and float-type sea level measurement systems have a measurement range of about 20 meters from the surface of the sea. However, if ground movement occurs due to an earthquake or other phenomenon, it becomes difficult to measure sea levels. In fact, ground movement due to a major earthquake that occurred on the Noto Peninsula of Japan in January 2024 disabled measurement equipment along part of the coastline, resulting in a delay before reliable measurements could be resumed.

About the New Technology

This new technology delivers 3D-LiDAR infrared laser beams to buoys floating on the sea, and reflected light is used to measure the distance. This ultra-sensitive optical reception is accomplished using long-range 3D-LiDAR with advanced long-range, large-capacity optical transmission and reception technology (coherent reception technology), making it possible to obtain the 3D point cloud data of objects from greater distances. As a result, this is the first time that sea levels have been successfully measured from a distance of 60 meters from the sea with an error of about 2cm. In addition, a 3D water level measurement technology has been developed that clusters processing of the acquired 3D point cloud data, classifies the shape of buoys and surrounding topography with high precision, and then compares the information to correct the position and estimate the height of buoys. This makes it possible to measure from a variety of locations and angles, meaning that 3D-LiDAR equipment can be installed in a wider variety of locations.

3D point cloud data scanned by 3D-LiDAR

As a result, tide stations may be installed in locations along the coastline that are less susceptible to significant ground movement, making the system disaster-resistant and enabling continuous monitoring of sea levels. In addition, the equipment is portable and may be flexibly installed across a wide range of locations, helping to reduce installation costs and time.

Future Developments

Going forward, NEC plans to continue developing this technology, including extending the measurable distance to several hundred meters and improving measurement accuracy by comparing 3D-LiDAR data with map information of the surrounding area, aiming for practical application by the end of FY2025.