Patent ID: 8810649

Claim:
A method of navigation in a mobile device using a reference wall, the method comprising: determining a reference angle (θ REF ) of the reference wall, comprising: determining a building containing the reference wall; finding the building on an overhead map; and computing the reference angle (θ REF ) from the overhead map; capturing, with a camera in the mobile device, a local image containing a horizontal feature; processing the local image to determine a horizontal feature angle (θ HF ), wherein the horizontal feature angle (θ HF ) measures an angle from a current orientation of the mobile device to the horizontal feature; selecting a wall angle, of the horizontal feature, equal to an integer multiple of 90° from the reference angle (θ REF ); and determining an angle of the current orientation of the mobile device based on a combination of the horizontal feature angle (θ HF ) and the wall angle.