A method, performed by circuitry in a rover , useful in determining relative position of the rover having a global positioning system, GPS, receiver, using information from a plurality of satellites and a plurality of base receivers , comprising: receiving position related information from a plurality of satellites ; receiving further position related information from each of the plurality of base receivers ; determining double-differenced widelane float ambiguity estimates, and their associated covariance matrices, for a plurality of pairs, each pair including the rover and a different base receiver based on the position related information and the further position related information; determining groups of candidate widelane integer ambiguities and their associated covariance matrices, each of the groups being for a base receiver of interest and a satellite of interest, each group including candidate widelane integer ambiguities for the receiver of interest and each of the plurality of satellites, including the satellite of interest, and candidate widelane integer ambiguities for at least some other base and the satellite of interest; performing a first test to determine, for at least one group, on a rover/base receiver pair basis for the plurality of satellites, if the candidate widelane integer ambiguities exhibit a statistical distribution consistent with low noise phase measurements; performing a second test to determine, for at least one group, on a single satellite basis for a plurality of rover/base receiver pairs, if the candidate widelane integer ambiguities exhibit a statistical distribution consistent with low noise phase measurements; and selecting, from among the candidate widelane integer ambiguities that have passed both the first test and the second test, a widelane integer ambiguity for use in determining relative position of the rover , wherein statistics of the first test and the second test are decorrelated from one another. receiving position related information from a plurality of satellites ; receiving further position related information from each of the plurality of base receivers ; determining double-differenced widelane float ambiguity estimates, and their associated covariance matrices, for a plurality of pairs, each pair including the rover and a different base receiver based on the position related information and the further position related information; determining groups of candidate widelane integer ambiguities and their associated covariance matrices, each of the groups being for a base receiver of interest and a satellite of interest, each group including candidate widelane integer ambiguities for the receiver of interest and each of the plurality of satellites, including the satellite of interest, and candidate widelane integer ambiguities for at least some other base and the satellite of interest; performing a first test to determine, for at least one group, on a rover/base receiver pair basis for the plurality of satellites, if the candidate widelane integer ambiguities exhibit a statistical distribution consistent with low noise phase measurements; performing a second test to determine, for at least one group, on a single satellite basis for a plurality of rover/base receiver pairs, if the candidate widelane integer ambiguities exhibit a statistical distribution consistent with low noise phase measurements; and selecting, from among the candidate widelane integer ambiguities that have passed both the first test and the second test, a widelane integer ambiguity for use in determining relative position of the rover , wherein statistics of the first test and the second test are decorrelated from one another. <EOS>