A GNSS device comprising: a receiver including a tilt sensor capable of measuring a tilt, an electronic compass capable of measuring a direction, a GNSS antenna capable of acquiring positional information; a pole attached to the receiver said receiver being supported on a center of a horizontal surface provided at the pole at an upper end of the pole, said center being on the vertical line of a ground contact point (P) of the pole; a controller including a touch-panel type display unit and an arithmetic control unit 35 that calculates highly accurate three-dimensional positioning data coordinates of an installation point (O) of the receiver and calculates the coordinates of the ground-contact point (P) of the pole from the calculated three-dimensional positioning data coordinates and the detection results of the tilt sensor and the electronic compass and the vertical height (Ah) of the pole; wherein, during real-time kinematic (RTK) observation, as a RTK observation screen, the display unit displays a mark that denotes a known point , a mark that denotes the GNSS device's own observation point , an electronic bubble tube with a bubble in a color corresponding to a level of the tilt measured by the tilt sensor, and the three-dimensional positioning data coordinates , wherein, while the GNSS antenna acquires positional information during RTK observation, when the tilt sensor or the electronic compass requests calibration for adjustment, an icon urging calibration is displayed on the display unit, and when the icon is tapped, the screen of the display unit shifts to a calibration screen. a receiver including a tilt sensor capable of measuring a tilt, an electronic compass capable of measuring a direction, a GNSS antenna capable of acquiring positional information; a pole attached to the receiver said receiver being supported on a center of a horizontal surface provided at the pole at an upper end of the pole, said center being on the vertical line of a ground contact point (P) of the pole; a controller including a touch-panel type display unit and an arithmetic control unit 35 that calculates highly accurate three-dimensional positioning data coordinates of an installation point (O) of the receiver and calculates the coordinates of the ground-contact point (P) of the pole from the calculated three-dimensional positioning data coordinates and the detection results of the tilt sensor and the electronic compass and the vertical height (Ah) of the pole; wherein, during real-time kinematic (RTK) observation, as a RTK observation screen, the display unit displays a mark that denotes a known point , a mark that denotes the GNSS device's own observation point , an electronic bubble tube with a bubble in a color corresponding to a level of the tilt measured by the tilt sensor, and the three-dimensional positioning data coordinates , wherein, while the GNSS antenna acquires positional information during RTK observation, when the tilt sensor or the electronic compass requests calibration for adjustment, an icon urging calibration is displayed on the display unit, and when the icon is tapped, the screen of the display unit shifts to a calibration screen. <EOS>