1. A method of determining landmarks, the method comprising: receiving, at a computing system, a plurality of potential landmark measurements and corresponding signal measurements; determining, at the computing system, a plurality of landmark candidates from the plurality of potential landmark candidates and corresponding signal measurements; determining, at the computing system, a normalized signal distance between a first signal measurement corresponding to a first landmark candidate of the plurality of landmark candidates and a second signal measurement corresponding to a second landmark candidate of the plurality of landmark candidates; and determining, at the computing system, that the first landmark corresponds to the second landmark based on the normalized signal distance.