PURPOSE: To measure the pitch angle and azimuth angle of a marine vessel in a short time with high accuracy by utilizing outputs of the 1st and the 2nd GPS gyros provided on the bow-stern axis of the marine vessel.

CONSTITUTION: The 1st GPS1 is provided at the bow position A on the bow- stern axis of the marine vessel S and the 2nd GPS2 is provided at the stern position B. The GPSs are radio wave navigation devices which receive range data from plural satellites and decide on the position and speed of their vessel. Output data of the GPS1 and GPS2 are inputted to a speed and position arithmetic part 3 and also inputted to a pitch angle and azimuth angle arithmetic part 4. Consequently, measured values of the pitch angle and azimuth angle are obtained accurately without using any dedicated measuring instrument and the 3rd GPS5 is further provided to measure the roll angle.