Abstract: A method of processing signal data including an unencrypted portion and an encrypted portion, the method including: receiving, at a receiver, the signal data; processing a sample of the signal data to provide a processed signal sample including data relating to the encrypted portion of the signal data and data relating to the unencrypted portion of the signal data, comparing the unencrypted signal data with at least one reference signal to determine information including at least one of (i) the time at which the signal was sent from the source and (ii) the identity of the source; requesting, based on the determined information, and from a source remote to the receiver, a set of encrypted reference signal samples; comparing, on a processing device remote to the receiver, the set of encrypted reference signal samples with the received encrypted signal data to identify any matching signal samples.

Abstract: A method and apparatus for signal weighting for satellite navigation systems is described. The method comprises (i) receiving secure and open service signals from at least one satellite navigation system, (ii) for received signals, determining a pseudo-range, and (iii) associating a statistical weighting to each pseudo-range, said weighting comprising a consideration of whether the signal is an open signal or a secure signal.

Abstract: A method of processing signal data including an unencrypted portion and an encrypted portion, the method including: receiving, at a receiver, the signal data; processing a sample of the signal data to provide a processed signal sample including data relating to the encrypted portion of the signal data and data relating to the unencrypted portion of the signal data, comparing the unencrypted signal data with at least one reference signal to determine information including at least one of (i) the time at which the signal was sent from the source and (ii) the identity of the source; requesting, based on the determined information, and from a source remote to the receiver, a set of encrypted reference signal samples; comparing, on a processing device remote to the receiver, the set of encrypted reference signal samples with the received encrypted signal data to identify any matching signal samples.