The present invention is a standalone motion tracking device using Linear Optical Sensor Arrays (LOSA). The invention constitutes a tracker module and an active marker, which communicate with each other wirelessly. The motion tracking device uses optical tracking along with inertial sensing to estimate the position and attitude of the active marker relative to the tracker module. The system determines the position of the active marker using stereovision triangulation through multiple views emanating from different LOSA modules. The present invention also features novel use of a multi-slit aperture for LOSA sensors in order to increase the field of view and resolution of the position estimates. The system uniquely leverages the structural geometry of the active marker, along with inertial sensing, to estimate the attitude of the active marker relative to the tracker module without relying on magnetic sensing that may often be unreliable.