A system and method for optically tracking a mobile device uses a first displacement value along a first direction and a second displacement value along a second direction, which are produced using frames of image data of a navigation surface, to compute first and second tracking values that indicate the current position of the mobile device. The first tracking value is computed using the second displacement value and the sine of a tracking angle value, while the second tracking value is computed using the second displacement value and the cosine of the tracking angle value. The tracking angle value is an angle value derived using at least one previous second displacement value.