A survey system comprising: a prism device including a reflecting prism; and a surveying instrument including a horizontal drive section for horizontally rotating a collimating telescope, a vertical drive section for vertically rotating the collimating telescope, and control means for controlling both drive sections, wherein the prism device comprises a prism-side GPS receiver for detecting a position, an atmospheric pressure sensor for detecting an atmospheric pressure, and a prism-side transmitter and receiver section for communicating with the surveying instrument, the surveying instrument comprises a surveying instrument-side GPS receiver for detecting a position and a surveying instrument-side transmitter and receiver section for communicating with the prism device, and the control means of the surveying instrument is configured for detecting and storing an atmospheric pressure at the position of the surveying instrument by use of the atmospheric pressure sensor with the prism device made adjacent beforehand to the surveying instrument placed on a reference point, the control means includes azimuth angle and distance calculating means for calculating both of an azimuth angle of the prism device when viewed from the surveying instrument and a distance between the surveying instrument and the prism device from the position of prism device and the position of the surveying instrument, elevation angle calculating means for calculating an elevation angle of the prism device when viewed from the surveying instrument from the distance and the atmospheric pressure at the position of the prism device and the atmospheric pressure at the position of the surveying instrument, and rotation command means for issuing a rotation command to the horizontal drive section and the vertical drive section so that the collimating telescope is directed toward the prism device based on the azimuth angle and the elevation angle. a prism device including a reflecting prism; and a surveying instrument including a horizontal drive section for horizontally rotating a collimating telescope, a vertical drive section for vertically rotating the collimating telescope, and control means for controlling both drive sections, wherein the prism device comprises a prism-side GPS receiver for detecting a position, an atmospheric pressure sensor for detecting an atmospheric pressure, and a prism-side transmitter and receiver section for communicating with the surveying instrument, the surveying instrument comprises a surveying instrument-side GPS receiver for detecting a position and a surveying instrument-side transmitter and receiver section for communicating with the prism device, and the control means of the surveying instrument is configured for detecting and storing an atmospheric pressure at the position of the surveying instrument by use of the atmospheric pressure sensor with the prism device made adjacent beforehand to the surveying instrument placed on a reference point, the control means includes azimuth angle and distance calculating means for calculating both of an azimuth angle of the prism device when viewed from the surveying instrument and a distance between the surveying instrument and the prism device from the position of prism device and the position of the surveying instrument, elevation angle calculating means for calculating an elevation angle of the prism device when viewed from the surveying instrument from the distance and the atmospheric pressure at the position of the prism device and the atmospheric pressure at the position of the surveying instrument, and rotation command means for issuing a rotation command to the horizontal drive section and the vertical drive section so that the collimating telescope is directed toward the prism device based on the azimuth angle and the elevation angle.