Method and apparatus for determining device location

Abstract

A satellite-based positioning system is provided that is configured to combine non-concurrent sets of pseudoranges all taken at a common location to determine at least a 2D position of the common location.

We claim: 
     
         1 . A method of combining non-concurrent pseudoranges, comprising:
 obtaining a plurality of non-concurrent pseudorange sets corresponding to a common location, wherein each set comprises a concurrent pair of pseudoranges or a concurrent triplet of pseudoranges; and solving for at least a 2D position of the common location using the plurality of non-concurrent pseudorange sets.   
     
     
         2 . The method of  claim 1 , wherein solving for at least a 2D position comprises solving for a 3D position of the common location. 
     
     
         3 . The method of  claim 1 , wherein each non-concurrent pseudorange set comprises a concurrent pair of pseudoranges. 
     
     
         4 . A method of building a database, comprising: receiving a wireless proxy for a current location of a receiver and a pseudorange from the receiver; associating the wireless proxy with non-concurrent pseudoranges having similar wireless proxies; and determining a 3D or 2D position of the receiver using the pseudorange and the non-concurrent pseudoranges.