Correlating Overlapping Magnetic Measurement Data from Multiple Magnetic Navigation Devices and Updating a Geomagnetic Map with that Data

In one embodiment, a method includes receiving from one or more magnetic-measurement devices one or more trajectories comprising magnetic measurements in an area collected by the magnetic-measurement devices over a period of time. The method also includes performing one or more correlation analyses on at least some of the trajectories to determine similarities in the trajectories. The method also includes storing portions of the trajectories that have determined similarities below predetermined thresholds for incorporation into a master geomagnetic map.