Friday, March 18, 2011

Japan and its effects on GPS and Geodata

The massive earthquake (magnitude 9.0 Richter scale) in Japan has caused a shift of a land mass of the peninsula Honshu. The land mass of Japan biggest main island was shifted by an average of 2.5 meters. The Earth’s axis has also shifted slightly.


The world's fifth-largest, 8.9 magnitude quake was caused when the Pacific tectonic plate dove under the North American plate, which shifted Eastern Japan towards North America by about 13 feet. The quake also shifted the earth's axis by 6.5 inches, shortened the Earths day by 1.6 miliseconds, and sank Japan downward by about two feet.

For this reason also spatial data of Japan has to be updated. Data form TomTom or Navteq used in navigational devices has to be updated in order to provide a correct matching of streets in reality and navigational data. The accurency of commercial GPSL systems will be defined with 10 meters. The software will therefore compensate inaccuracies for mainstream use. In the field of high precision suveys and differential GPS the shift of land masses will have an impact.
Around 1200 GPS ground stations are in operation in Japan. They are used for geographic survey of the country and deliver correction data for GPS signals received.
It is not assumed that there is any impact of the airborne part of the GPS system. In theory, the displacement of the Earth’s axis result in a change of gravity and this would affect the orbit of the satellites. But the orbit of the GPS satellites is very high and therefore hardly affected.






Look at following map to see the horizontal shift:
http://www.esri.com/services/disaster-response/japan-earthquake-tsunami-2011-map/shift-map.html

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