Abstract: A position detection device for detecting the position of a bucket of an excavator having a cab and one or more booms is disclosed. A boom is rotatably attached to the cab by a mounting structure that is rotatably attached to the cab by a shaft having a longitudinal axis extending basically vertically during normal use of the excavator. The bucket is rotatably mounted to a stick that is rotatably attached to the boom. The mounting structure is arranged and configured to allow the boom to be rotated with respect to the longitudinal axis of the shaft. The position detection device comprises one or more antennas arranged and configured to receive satellite signals. The position detection device comprises a sensor assembly configured to detect the angular position of the boom with respect to rotation about the longitudinal axis of the shaft.