US Patent 9476717 Simultaneous localization and mapping by using Earth's magnetic fields

There is provided an apparatus configured to perform operations comprising: acquiring motion data sets from the plurality of mobile devices; estimating route models of the traveled routes on the basis of the motion data sets; generating EMF fingerprints for the traveled routes by associating the acquired EMF data sets with corresponding points of the route models; and determining the locations of the routes with respect to each other on the basis of at least one of the following: the EMF fingerprints and the route models.