An integer ambiguity resolution method includes: receiving SPS signals; determining, for the SPS signals, candidate float ambiguity values indicative of float numbers of carrier signal wavelengths of the SPS signals between respective satellite sources, of the SPS signals, and the mobile device; and performing, in response to failure of an integer ambiguity resolution validation check based on at least a first subset of the candidate float ambiguity values, an integer ambiguity search using at least a second subset of the candidate float ambiguity values; wherein each candidate float ambiguity value of the at least second subset of the candidate float ambiguity values corresponds to a second indication of candidate float ambiguity accuracy that is higher than a first indication of candidate float ambiguity accuracy, if any, corresponding to the at least first subset of the candidate float ambiguity values.