SURVEY SYSTEM USING GPS

PROBLEM TO BE SOLVED: To freely change the height of a GPS(global positioning system) antenna, and accurately measure the height of a ground at all times, regardless of such a disturbance as change in antenna height and subsoil slope. SOLUTION: In a case where radiowave from a satellite cannot be received due to dense trees or the like around the measuring point, the rod part 18B of an antenna elevator device 18 is extended upward, thereby heightening the position of a GPS antenna 14. This antenna 14 and a rod 30 are held with a universal joint 28, and the rod 30 is always kept in the vertical direction. Also, a laser range finding device 34 emits laser beams in the downward vertical direction, and measures the distance to the ground LS. A personal computer 22 substrates a distance from the antenna 14 to a rod end L1 and the distance LS from the height of the antenna 14 measured with a GPS body 16, thereby calculating the height of a ground immediately below the antenna 14. According to this construction, ground height can be provided, even when the ground has a slope, due to the use of distance LS measured with the laser range finding device 34.