The Railway Technical Research Institute has developed a position detection system based on a new Global Positioning System (GPS). This system uses GPS to detect the approximate location of a train and then selects one of three algorithms to process the location data and determine the train's precise location. Running tests performed on the system showed that its position error was less than 4 m. This system has the potential to be used to control the car body tilting of tilt trains accurately and allow them to run at the maximum possible speed through the tight curves typical of the narrow-gage lines found in Japan. In addition, the automatic map created by this system makes it much easier to maintain the accuracy of the onboard database.