Abstract: Methods and systems employ at least two motion estimators to form respective estimates of position of a mobile device over time. The estimates of position over time are based on sensor data generated at the mobile device. Each motion estimator is associated with a respective reference frame, and each respective estimate of position includes one or more estimate components. A transformation from the reference frame associated with a second motion estimator to the reference frame associated with a first motion estimator is determined. The transformation is determined based at least in part on at least one estimate component of the one or more estimate components of the estimates of position formed by each of the first and second motion estimators.

Abstract: Methods and systems estimate calibration errors of magnetic sensor measurements collected at mobile devices. Each measurement is associated with a location of one of the mobile devices and has a calibration error. Data from the sensor measurements is partitioned into sets. Each set is associated with a respective calibration error associated with the measurements that generated the data in the set. Pairs of data items are identified, where each pair includes a data item from a first of the sets corresponding to a measurement, associated with a first location, that generated the data in the first set, and a data item from a second of the sets corresponding to a measurement, associated with a second location that is approximately the same as the first location, that generated the data in the first set. The calibration error associated with each of the sets is estimated based in part on the pairs.