System and process of determining vehicle attitude
A system and process that can be used to determine vehicle attitude with only one navigation receiver. In one embodiment, the antenna of the navigation receiver is driven with a signal that modulates sensitivity in azimuth. The received navigation signal strength is demodulated by the phase at which the antenna is sweeping and a phase angle and a magnitude for the incoming signal are calculated. Using this calculated phase angle, magnitude and antenna characteristics, the location of the user (i.e. the navigation receiver) and the location of the navigation satellite, the attitude of the antenna and hence the user or user vehicle can be determined.
1. A process of determining vehicle attitude using one or more navigation satellites, comprising:
modulating the sensitivity of a single antenna of a single Global Positioning System (GPS) receiver in azimuth;
using the GPS receiver to receive a navigation signal from at least one navigation satellite;
demodulating the navigation signal by a phase at which the sensitivity of the single antenna is modulated in azimuth and determining a phase angle for the incoming signal;
determining the location of the GPS receiver;
determining the location of the one navigation satellite; and
determining the vehicle attitude of the vehicle using the phase angle, the location of the GPS receiver and the location of the one navigation satellite.
2. The process of claim 1 , further comprising:
using the GPS receiver to receive multiple navigation signals from multiple navigation satellites;
determining a phase angle for each of the incoming signals;
determining the location of each navigation satellite; and
determining the attitude of the vehicle using the phase angles, the location of the GPS receiver and the locations of the navigation satellites.
3. The process of claim 1 , the GPS receiver receiving a plurality of navigation signals, and further comprising determining if the navigation signals are coming from a wrong angle or if the navigation signals are all coming from the same angle.
4. The process of claim 1 , further comprising determining the vehicle attitude of the vehicle using the phase angle, the location of the GPS receiver and the location of only the one navigation satellite.
5. The process of claim 1 , further comprising determining the vehicle attitude of the vehicle using only the phase angle when the vehicle is at least one of: known to be local level given vehicle characteristics; and aided by an Inertial Measurement Unit (IMU).
6. The process of claim 1 , wherein determining the vehicle attitude of the vehicle includes estimating an elevation based on an interference pattern.
7. The process of claim 1 , further comprising creating an interference pattern, wherein determining the vehicle attitude of the vehicle includes using the created interference pattern.
8. The process of claim 1 , further comprising determining one of the azimuth and the phase angle based on an antenna gain, an elevation of the navigation signal with respect to the vehicle, an elevation of the navigation signal with respect to the single antenna, an antenna tilt angle of the single antenna with respect to the vehicle level, an angular rate of antenna sensitivity rotation.
9. The process of claim 1 , further comprising determining the azimuth when the single antenna is in a static antenna pattern.
10. The process of claim 9 , further comprising determining the azimuth when the single antenna is in a static antenna pattern using a signal strength of the single antenna, a single strength of a second antenna, a gain of the single antenna, and a gain of the second antenna.