Currently, various devices which calculate a traveling state of a movable body using GPS signals have been in practical use. For example, an attitude calculating device disclosed in Patent Document 1 includes four GPS antennas. Lengths of base lines (base lengths) which respectively connect the four antennas are different.
The attitude calculating device disclosed in Patent Document 1 may be selected two antennas which are in a receiving state in which positioning is possible and have the longest base length. The attitude calculating device disclosed in Patent Document 1 calculates an attitude by using the GPS signals received by the two GPS antennas.