Abstract-An algorithm for integrating foot-mounted inertial sensor platforms is presented. The proposed integration scheme is based on a cascaded estimation architecture. A lower Kalman filter is used to estimate the step-wise change of position and direction of one or optionally both feet respectively. These estimates are used in turn as measurements in an upper particle filter, which is able to incorporate nonlinear map-matching techniques. To ease the integration of both feet a simple mechanical pedestrian model is developed. The proposed algorithm is verified using computer simulations and experimental data.