CACam: Consecutive Angular Measurements with Camera on Smartphone for Distance Estimation

To estimate the distance between a user and the target object for personal interest or for subsequent actions, the commonly used method is to search the target in the map application. However this is limited by GPS signal status under different environments and incomplete information on the map application of smartphones. This paper introduces a ranging method, CACam, which utilizes consecutive angle measurement based on camera of smartphone. Geometric model and ranging process are proposed to calculate the distance. When the user aligns the target from different position points, we record readings from the gyroscope sensor during every rotation in the procedure. The camera is used for aligning the target to build geometric model. Vector mapping of angular readings and data processing of intermediate points are used to get more accurate angles, which is suitable for the situation that the smartphone could not be strictly rotated in perpendicular to the plane of the gravity. The effectiveness of our ranging method is verified through experiments in outdoor environments.