Multipath mitigation for GNSS location determination using dual antennas

A system comprising:

• a movable structure;
• a first antenna and a second antenna mounted to the movable structure at a fixed baseline distance apart, the fixed baseline being between 10 cm and 30 cm, the first antenna and the second antenna being configured to receive global navigation satellite system (GNSS) signals from each at least four GNSS satellites, wherein the GNSS signals received from each of the at least four GNSS satellites include a plurality of GNSS signals having different frequencies and wherein the GNSS signals received from each of the GNSS satellites include signals at three or more different frequencies;
• receiver circuitry coupled to the first antenna and the second antenna and configured to extract a first set of observables from a first GNSS signal from a first one of the GNSS satellites as received by the first antenna and a second set of observables from the first GNSS signal as received by the second antenna, wherein the first set of observables includes a first carrier phase at each of the different frequencies and the second set of observables includes a second carrier phase at each of the different frequencies;
• and
• a signal processing engine coupled to the receiver circuitry and configured to:
• receive respective first and second sets of observables from the receiver circuitry for each of the at least four GNSS satellites;
• compute, for each of the at least four GNSS satellites and each frequency, a first frequency-specific single difference carrier phase (SDCP) between the second carrier phase and the first carrier phase;
• compute, for each GNSS satellite, a geometry-free SDCP based on the frequency-specific SDCPs at two different frequencies, wherein the computing includes determining at least three geometry-free SDCPs, wherein each of the at least three geometry-free SDCPs is based on a different pair of the frequencies;
• determine, based on the geometry-free SDCPs, for each of the at least four GNSS satellites an estimate of a multipath effect for the GNSS satellite from which the GNSS signal was received, wherein the determining includes determining a respective estimate of a multipath effect based on each of the geometry-free SDCPs;
• compare the respective estimates of the multipath effect to identify a frequency that is experiencing multipath error;
• assign a weight for each of the GNSS satellites based at least in part on the first SDCP the estimate of the multipath effect for each GNSS satellite, wherein the weight is assigned according to a continuously-valued function that decreases with increasing estimated multipath effect and wherein a lower weight is assigned to observables extracted from GNSS signals at the frequency that is experiencing multipath error;
• and
• determine a location of the movable structure using the weight and the respective first and second sets of observables from the at least four GNSS satellites.