1. A method comprising, at a mobile device: obtaining three-dimensional geographic information identifying at least one open area and at least a height associated with at least one object adjacent to the at least one open area; determining at least one pathway in said open area; determining expected line of sight and expected non-line of sight detections of satellite positioning system (SPS) signals at locations along said pathway based, at least in part, on said three dimensional geographic information; acquiring one or more signals at a receiver; and estimating a location of said mobile device based, at least in part, on application of said expected line of sight detections and expected said non-line of sight detections to said acquired signals.