PURPOSE: To modify setting conditions such as a prediction horizontal position error (FOM value) etc., and to obtain a GPS navigation system for checking whether the position-measurement data with a required accuracy are obtained or not by providing a display for showing the judgment result of the accuracy of position measurement data and a means for switching a display means.
CONSTITUTION: A GPS signal from a GPS satellite is received by the signal reception antenna of a GPS sensor 1 and is subjected to signal processing. At this time, FOM value indicating the signal reception state is calculated from the detected position measurement data. The FOM value is compared with the display conditions of a preset display 2, an LED is lit when the FOM value is included in the display conditions, and then it is reported to a user that the position measurement data are calculated within a required accuracy. If a position is different from an actual position even if the LED lights up, a PC(Personal Computer) 5 is connected to a GPS sensor 1 and the display conditions of the display 2 are switched with a high accuracy. If the LED does not light up, the installation location of the GPS sensor 1 is modified.
BANDO TAKASHI
TAKEDA HIROSHI
MAEDA AKITSUGU
USAGAWA MICHINOBU
