Abstract: A system for monitoring operation and location of a first moving vehicle relative to a second moving vehicle. A minimum separation distance between the first and second vehicles is estimated, based on the first vehicle velocity, and optionally on the second vehicle velocity, using location determination (LD) signals received from satellite-based transmitters from GPS, GLONASS and LEO satellites, or from ground-based signal sources such as LORAN signal towers, and using ranging signals from SONAR, RADAR or a similar system. The minimum separation distance is compared with the actual separation distance at selected times, and a vehicle driver is advised if the actual separation distance is too small, if the separation distance is decreasing too quickly, or if the second vehicle velocity is decreasing too quickly. The second vehicle may travel in the same traffic lane, in an adjacent lane, or on a road that intersects the road used by the first vehicle.

Abstract: A system for monitoring operation and location of a moving first vehicle relative to a second vehicle. A minimum separation distance between the first and second vehicles is estimated, based on the first vehicle velocity, and optionally on the second vehicle velocity, using location determination (LD) signals received from satellite-based transmitters from GPS, GLONASS and LEO satellites, or from ground-based signal sources such as LORAN signal towers, and using ranging signals from SONAR, RADAR or a similar system. The minimum separation distance is compared with the actual separation distance at selected times, and a vehicle driver is advised if the actual separation distance is too small, if the separation distance is decreasing too quickly, or if the second vehicle velocity is decreasing too quickly. The second vehicle may travel in the same traffic lane, in an adjacent lane, or on a road that intersects the road used by the first vehicle.

Abstract: A first receiver computes its position using data from sources chosen according to conditions at a second receiver and reference data. The computed position is compared with a known position. The data may be GPS positioning data from satellites and/or pseudolites and the reference data may be RTK GPS data provided by an RTK GPS reference station. The conditions at the second receiver generally correspond to satellite constellations and other parameters and the position of the first receiver may be computed by configuring the first receiver to mimic the conditions at the second receiver. The comparison of the computed position to the known position may result in an error measurement which may be used to initiate an alert condition. In a further embodiment, a receiver has first circuitry configured to compute its position using data from sources chosen according conditions at a remote receiver and reference data.