A method comprises receiving a plurality of signals from a plurality of space-based satellites, wherein the plurality of space-based satellites comprises at least one space-based satellite from each of a plurality of Navigation Satellite System (NSS) constellations. The method also comprises determining, in a first domain, a first plurality of sub-solutions based on a respective sub-set of the plurality of signals, each respective sub-set in the first domain chosen according to a characteristic defining the first domain; and determining, in a second domain, a second plurality of sub-solutions based on a respective sub-set of the plurality of signals, each respective sub-set in the second domain chosen according to a characteristic defining the second domain. The method further comprises determining if an error is present in the navigation system based on the first plurality of sub-solutions and on the second plurality of sub-solutions.