A measurement agent for measuring a distance from the agent to a tag may include a transmitter and receiver for transmitting and receiving radio wave signals. Gas introduced into the housing assembly by rotation of the impeller is compressed at least by centrifugal force. Target coordinates of the target in relation to the rotation center of the surveying instrument are then determined based on the first camera position and orientation, the first image coordinates, the second camera position and orientation, the second image coordinates, and first and second camera calibration data. The receiver includes a receiving antenna located at such a predetermined position on a body of the vehicle that all distances from the receiving antenna to the rotation axes of the wheels of the vehicle are different from each other. The recess is formed in the rear end of the block between the lugs.