Abstract: The invention is directed to an electro-optical rangefinding-type apparatus which uses electronic sensors to detect the position and orientation of the apparatus relative to a fixed point. Data from the sensors is relayed to a microprocessor which can calculate parameters such as range, horizontal distance and angle, vertical distance and angle, relative speed and magnetic bearing of a target objective, which are then displayed. A preferred embodiment of the invention is convertible between the functions of a stereoscopic binocular and a coincidence-type range-finder and means are provided for converting the apparatus to and from the binocular and rangefinding modes.