Linear and rotational speeds of a mobile device are calculated using distance estimates between imaging sensors in the device and objects or scenes in front of the sensors. The distance estimates are used to modify optical flow vectors from the sensors. Shifting and rotational speeds of the mobile device may then be calculated using the modified optical flow vector values. For example, given a configuration where the first imaging sensor and the second imaging sensor face opposite directions on a single axis, a shifting speed is calculated in the following way: multiplying a first optical flow vector and a first distance estimate, thereby deriving a first modified optical flow vector value; multiplying a second optical flow vector and a second distance estimate, thereby deriving a second modified optical flow vector value; the second modified optical flow vector value may then be subtracted from the first modified optical flow vector value, resulting in a measurement of the shifting speed.