To obtain a relative localization between a plurality of mobile devices, a first mobile device observes a second mobile device within a field of view of the first mobile device's camera at time t1, determines a first position of the first mobile device at t1, and receives from the second mobile device a second position of the second mobile device at t1. The first mobile device determines information about the first mobile device's orientation with respect to the second mobile device at t1 based at least in part on the first position and the observation of the second mobile device. The first mobile device identifies two constraints that relate the mobile devices' coordinate systems based at least in part on the second position and the orientation information. The first mobile device's pose relative to the second mobile device may be calculated once at least six constraints are accumulated.