A portable area monitoring system for use with a horizontal directional drilling machine and adapted to produce a composite of the positions of a beacon and a fixed object. In a preferred embodiment the sensor assembly is supported by a hand-held frame and adapted to detect signals emanating from each of a beacon and a fixed object. The sensor assembly transmits the detected signals to a processor which simultaneously processes the signals to produce a composite of relative positions of the beacon and the fixed object to the frame. The composite of the relative positions of the beacon and the fixed object to the frame is communicated to the operator using a portable display.