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Remote Sensing Technology Center of Japan

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Detecting Dangerous Spots in Social Infrastructure in their early stages. Contributing to Ensure a Safe, Secure and Robust Society

Ryoichi Furuta

By 2025, social infrastructure such as roads, constructed during Japan’s period of rapid economic growth, will be around 50 years old. Comparing it to the lifespan of a human being, it is now entering “the phase of an aging society.” If a major earthquake struck, this infrastructure could collapse, and there is an urgent need to detect dangerous sites in order to extend their lifespan. Using satellites allows expansive areas to be surveyed to identify dangers and distortions in building structures on a scale of several millimeters to several centimeters.

Ryoichi Furuta, Infrastructure Team Leader

Detecting land deformation in the area around Tokyo Bay from SAR data
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(A-1) Detecting land deformation in the area around Tokyo Bay from SAR data. The red indicates areas where an annual deformation of 2.5 cm has been detected. (A-2) Zooming in on an area where land deformation has been detected, and superimposing it onto road information allows identification of risk areas, and in turn efficient inspections and on-site surveys.

Monitoring a Wide Area All at Once. Zooming in on Danger Zones to a Scale of Millimeters

Social infrastructure such as railroads, roads, levees as well as water, gas and power facilities extend their networks across the entire country, covering long distances. This means they are difficult to replace with new systems once they have been laid down. However, they are deteriorating as they age year by year, and are in danger of falling apart as the result of earthquakes and land subsidence. Through visualizing dangerous locations, the degree of danger, and detecting risk areas early, the original strength of the social infrastructure can be maintained, and their lifetimes extended, by improving their ability to withstand disasters, and managing and preserving them.

Inspections are currently carried out in vehicles, manually by professionals, or based on reports from local residents. This requires a lot of time and money. Early detection of damage or risk areas requires streamlining the monitoring system. Using satellites allows extensive infrastructure networks to be covered all at once. Furthermore, using a Synthetic Aperture Radar (SAR) allows land deformation to be detected on a scale of several millimeters to several centimeters annually. For example, if a certain area is found to have experiences land deformation, it can be assumed that local buildings and infrastructure are at risk. Based on such assumptions, decisions can be quickly made to dispatch engineers to inspect the site. Moreover, the use of a high resolution satellite will allow deformation in the buildings themselves to be detected. For example, in the case of bridges, deformation due to heat can be monitored on a scale of millimeters to detect damage before any breakdown occurs. RESTEC is the only organization in Japan possessing this technology.

Land deformation is a problem that also affects artificial ground. It can also affect landfill sites for rubble left over from earthquakes, which there will no doubt be more of in the future. This problem is also expected to occur in developing countries where social infrastructure is currently under construction. Our aim is to engage in active research and development, and examine ways of creating a new service that can be put into practical use in Japan first, to contribute to establishing a safe, secure and robust social infrastructure. After accomplishing this, we hope to expand our service overseas.

September 20, 2009
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September 20, 2009

August 8, 2010
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August 8, 2010

Images taken during construction of Tokyo Gate Bridge. The image on the left was taken on September 20, 2009. The image on the right was taken on August 8, 2010. The process of constructing artificial structures and the ensuing environmental changes, and risks such as deformation of the land and the associated deformation of the artificial structure can all be monitored from observation satellites.

Detecting Landslides and Landslips Early to Help Prevent Secondary Disasters

Landslides are becoming more frequent by the year. Early detection of disasters is vital in securing evacuation routes and preventing secondary disasters. The land moves in landslides, and RESTEC has developed an analysis technique that can simultaneously detect landslides and landslips. Within only about 15 minutes of obtaining satellite data, the technique allows areas where landslides have occurred, as well as areas that are in danger of succumbing to landslides, to be simultaneously and accurately detected, providing information on potential secondary disasters and contributing to the drawing of hazard maps.

Image capturing massive landslides that occurred on Leyte Island in the Philippines in February 2006

Image capturing massive landslides that occurred on Leyte Island in the Philippines in February 2006. Red indicates the affected areas before the disaster, and green and blue indicate the areas affected after the disaster. It is often impossible to reach disaster-stricken areas immediately following a disaster, but satellite images enable the situation to be quickly grasped.