1. A computer implemented method of reconciling different entity identifiers of a same entity, the method comprising: receiving, by a processor, a plurality of series of location-time data items from a plurality of tracking systems that each track one or more entities, each series of location-time data items associated with an entity identifier; categorizing each location-data item into a space-time region; generating a track for each of the plurality of series of location-time data items based on the space-time regions into which the location-data items are categorized; generating a track signature for each of the generated tracks based on a segment of the generated track; comparing the track signatures to find matching track signatures; based on a plurality of matching signatures, reconciling the plurality of entity identifiers to a same entity; and responsive to determining a threshold number of tracks, generating a track signature for each of the generated tracks based on a shorter segment of the generated track, wherein the shorter segment is a different size than the segment of the generated track.