Multi-antenna GNSS positioning method and system
A multi-antenna GNSS system and method provide earth-referenced GNSS heading and position solutions. The system and method compensate for partial blocking of the antennas by using a known attitude or orientation of the structure, which can be determined by an orientation device or with GNSS measurements. Multiple receiver units can optionally be provided and can share a common clock signal for processing multiple GNSS signals in unison. The system can optionally be installed on fixed or slow-moving structures, such as dams and marine vessels, and on mobile structures such as terrestrial vehicles and aircraft.
1. A GNSS-based method of generating a navigation solution of a rover vehicle comprising the steps of:
providing a base receiver unit at a fixed location with a base GNSS receiver having a first clock, a base RF transmitter, and a base processor;
providing a base GNSS antenna connected to said base receiver;
providing a rover receiver unit with a rover GNSS receiver having a second clock, a rover RF receiver, and a rover processor;
providing a rover antenna array comprising multiple rover GNSS antennas, each connected to said rover receiver;
providing a stepper motor mounted on said vehicle and connected to said rover antenna array;
providing an encoder connected to said rover antenna array;
providing a gyroscope connected to said rover antenna array;
said rover processor receiving outputs from said encoder and said gyroscope;
providing said rover antenna array with multiple incremental orientations each corresponding to a portion of a full revolution;
programming said rover processor to rotate said stepper motor through said multiple incremental orientations relative to said vehicle;
adjusting the rotational speed of the stepper motor based on the rover vehicle velocity to receive ranging signals at intervals timed to the multiple, incremental orientations of the antenna array;
synchronizing the first and second clocks;
receiving GNSS signals at each of the base GNSS antenna and the rover GNSS antennas and respectively measuring carrier phase observations therefrom;
transmitting base receiver unit carrier phase observations using the base RF transmitter;
receiving said base receiver unit carrier phase observations using the rover RF receiver;
determining an attitude solution of said rover antenna array by solving for locations of the rover antennas with respect to each other on the basis of the base receiver unit carrier phase observations and the rover receiver unit carrier phase observations;
using said rover antenna array attitude solution to resolve global, carrier phase GNSS integer ambiguities at each antenna;
storing with said rover processor the attitudes and relative positions of said rover antenna array relative to said vehicle at said incremental orientations;
time-tagging and storing the relative antenna locations, antenna array attitude solution and carrier phase observations; and
said rover processor determining a position solution for said vehicle based on GNSS signals received by said rover antenna array, the time-tagged relative antenna locations, the antenna array attitude solution, received GNSS carrier phase observations, and said encoder and gyroscope outputs.
2. The method of claim 1 , which includes the additional steps of:
storing in the rover processor the determined position solutions for said vehicle at a plurality of spaced points in time.
3. The method of claim 2 , which includes additional steps of:
comparing the position and attitude solutions at first and second spaced points in time to provide an output representing movement of the vehicle based on rover vehicle antenna and antenna array position and attitude differences at said spaced points in time.