Japan’s government is backing a three-dimensional mapping system developed by Mitsubishi Electric Corporation that includes a wealth of details such as trees and pedestrians. It promises to be off by no more than 25cm (9.8 inches).

That would be a big improvement over satellite-based GPS, which is used by ships, aircraft and increasingly by drivers or on mobile phones but can be off by up to 20 metres (65 feet), especially inside buildings or underground.
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