US Patent 10386493 System and method for localization and tracking

A method of determining location of a user device includes receiving global navigation satellite system (GNSS) fix data that represents GNSS calculated position of the user device, receiving signal strength data associated with each satellite communicating with the user device, and receiving satellite data regarding locations of satellites. The method further includes retrieving satellite blocking values from a cache that describe a likelihood of a satellite signal being blocked at a plurality of possible locations. A non-linear filter, implemented by one or more processors, is applied to the GNSS fix data, signal strength data, and satellite blocking values to generate an updated position estimate of the user device.