PURPOSE: To enable accurate measurement of position, by computing the latitude, longitude and height of an operating object from a mean of height data and received data from three satellites.

CONSTITUTION: When an operating object 10 is running at a position 10, a receiving section 12 reproduces a satellite navigation message data and a pseudo distance data from radio waves of four satellites 14W41 received with an antenna 11. A position measurement computing section 13 prepares an equation of navigation from the data to determine the position of the operating object by calculating a distance to the position 101 and determines the moving speed and the bearing thereof by calculating a Doppler shift. At this point, the height data determined at the computing section 13 are inputted into a memory 16, where a fixed number of height data are stored while being updated. When radio waves from the satellite 42 become unable to be received as affected by an obstacle 7 such as a mountain during the running of the operating object 10 at a position 102, a plurality of height data stored in the memory 16 are read out with a mean calculating section 17 to calculate the mean thereof. Then, the position 102 is determined based on the mean of the height data calculated and signal datas from the three satellites 12W32.