Patent ID: 8160604

Claim:
A method of deriving a position estimate of a receiver from a plurality of parameter measurements, each of the plurality of parameter measurements measured concurrently at the receiver and derived from a respective actual correlation function that is derived by correlating a signal received at the receiver with an identification code uniquely identifying a corresponding transmitter, comprising: deriving a plurality of different estimates of a current position of the receiver, at least two of the plurality of different estimates of the current position of the receiver being derived with the same type of position-determination scheme, each of the different estimates derived from a subset of the plurality of parameter measurements, each of the plurality of parameter measurements measured by the receiver and each respective position estimate derived from a subset of the plurality of the parameter measurements that is different from other subsets of the plurality of parameter measurements used to derive other of the plurality of estimates of the current position of the receiver; deriving a cost of each of the position estimates; refining the costs based on local topography; and selecting one of the position estimates responsive to the refined costs.