Will This Happen Here? GPS Maps Way Off In Japan

Tokyo May 27, 2003; The Asahi Shimbun reported that it was a mystery that left drivers in island regions scratching their heads: On their in-car vehicle navigation system, drivers watched bewildered as their cars appeared to be motoring across the ocean when they were very definitely cruising along on solid ground.

Now the government's map-making institute has discovered the cause of the confusion: Numerous maps, including those used by many vehicle navigation systems, are wrong.

A survey by the Geographical Survey Institute (GSI) found small, remote islands in seven areas nationwide are incorrectly positioned on maps.

In some cases, the error is as large as about 800 meters, leading to mistakes with vehicle navigation systems.

The GSI plans to rectify the errors on maps since inaccuracies could cause traffic accidents, officials said.

``When I was driving on an island in Okinawa Prefecture, my vehicle navigation system indicated I was motoring along on the sea!'' said a driver quoted by a GSI official.

The results of the GSI survey will be announced at the Joint Meeting of Earth and Planetary Science, which runs from today through Thursday in Chiba.

According to the survey, which used Global Positioning System (GPS) technology for the first time to pinpoint the locations of remote isles, islands in seven of the 57 areas studied were incorrectly positioned on maps by more than 50 meters.

For example, the actual location of Iwojima island, which lies about 1,200 kilometers south of Tokyo, differed from its position on maps by as much as 793 meters-the equivalent of 3 centimeters on a map with a scale of 1:25,000.

In Okinawa Prefecture, the locations of Kita-Daitojima island and Minami-Daitojima island differed from their positions on maps by 642 meters.

Maps showed Taramajima island and Minnajima island to be 560 meters away from their actual positions, and the actual locations of Ishigakijima island and Taketomijima island differed from their positions on maps by 251 meters each.

Locations of remote islands were previously calculated by measuring the height of the polar star and other objects viewed from the islands.(IHT/Asahi: May 26,2003)