Making indoor maps with portable accelerometer and magnetometer

The paper describes algorithms required to enable the crowd sourcing of indoor building maps, i.e., where global positioning system (GPS) is not available. Nevertheless to enable crowd sourcing we use the 3-axis accelerometers and the 3-axis magnetometers available in many smart phones. Volunteers carry the phones while walking around in buildings, and use some application on their smart phones to send the data to a mapping server. We present the algorithms to obtain walking trajectories from the data by dead reckoning, and to estimate indoor maps with multiple walking trajectories.