MULTI-ANTENNA GNSS POSITIONING METHOD AND SYSTEM

• US 20090121932A1
• Filed: 01/08/2009
• Published: 05/14/2009
• Est. Priority Date: 03/20/2003
• Status: Active Grant

• Current Assignee: Hemisphere GNSS(USA) Incorporated
• Original Assignee: Hemisphere GNSS(USA) Incorporated
• Inventors: Whitehead, Michael L., Feller, Walter J.
• Granted Patent: US 8,686,900 B2
• Time in Patent Office: Days
• US Class Current: 342/357.360
• CPC Class Codes: A01B 69/008 automatic
• CPC Class Codes: G01S 19/14 specially adapted for specific applications
• CPC Class Codes: G01S 19/36 relating to the receiver frond end
• CPC Class Codes: G01S 19/43 using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry
• CPC Class Codes: G01S 19/51 Relative positioning
• CPC Class Codes: G01S 19/53 Determining attitude
• CPC Class Codes: G01S 19/54 using carrier phase measurements; using long or short baseline interferometry
• CPC Class Codes: G01S 5/0036 of measured values, i.e. measurement on mobile and position calculation on base station
• CPC Class Codes: G05D 1/0206 specially adapted to water vehicles
• CPC Class Codes: G05D 1/027 comprising intertial navigation means, e.g. azimuth detector inertial navigation G01C21/16; inertial navigation combined with non-inertial navigation instruments G01C21/165
• CPC Class Codes: G05D 1/0278 using satellite positioning signals, e.g. GPS

Abstract

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.

Claims

1. A GNSS method of determining an earth-referenced attitude and position of a structure, which method comprises the steps of:

providing a GNSS receiver;

providing multiple GNSS antennas connected to said receiver;

mounting said antennas on said structure;

constraining said antennas relative to said structure and each other based on fixed distance and geometry constraints;

receiving different GNSS signal multipath effects at respective different antenna locations;

providing a processor connected to said receiver;

said processor processing said GNSS antenna inputs for determining an earth-referenced attitude and position of said structure; and

said processor averaging said different GNSS signal multipath effects and thereby reducing or eliminating multipath errors from said GNSS-defined position of said structure.

2. The method of claim 1, which includes the additional steps of:

receiving common satellite signals at multiple said antennas; and

separating a pair of said antennas by a distance greater than the wavelength of the GNSS signals.

6. The method of claim 1, which includes the additional steps of:

providing an antenna input switch connected to said antennas;

connecting said antenna input switch to a receiver input; and

switching the receiver input among said antennas with said antenna input switch.

7. The method of claim 1, which includes the additional steps of:

providing multiple pairs of antennas; and

switching among said antenna pairs to mitigate multipath effects.

8. The method of claim 1, which includes the additional steps of:

providing an antenna rotating device;

providing a pair of antennas;

providing an antenna mounting structure and mounting said antennas thereon;

forming an antenna array with said antennas and said mounting structure;

mounting said antenna mounting structure on said rotating device between said antennas;

providing multiple predetermined antenna locations to obtain position and heading for said structure and to mitigate multipath effects;

locating said antenna locations at radially-spaced, predetermined intervals forming a circle around said rotating device; and

rotating said antennas among said antenna locations.

9. The method of claim 8, which includes the additional steps of:

providing said antenna rotating device with a stepper motor;

providing a stepper motor control connected to said processor; and

programming said processor to radially incrementally rotate said antenna array by actuating said stepper motor via said stepper motor control.

10. The method of claim 1, which includes the additional steps of:

providing an antenna rotating device;

providing an antenna mounting structure and mounting a pair of said antennas thereon;

forming an antenna array with said antennas and said mounting structure;

mounting said antenna mounting structure on said rotating device between said antennas;

providing an encoder connected to said antenna array;

providing a gyroscope connected to said antenna array; and

providing outputs from said encoder and said gyroscope to said processor for determining a position solution for said vehicle based on GNSS signals received by said antenna array.

11. The method of claim 1, which includes the additional steps of:

providing an orientation device mounted on said structure; and

said processor using an orientation of said structure for determining a position and heading solution.

12. The method of claim 1 wherein said receiver comprises a master receiver, which method includes the additional steps of:

providing a slave receiver;

connecting at least one of said antennas to each of said master and slave receivers respectively;

providing said receivers with either a common clock or synchronized clocks; and

receiving said GNSS signals at said receivers in unison and processing said GNSS signals with said processor in unison by operation of said common clock or synchronized clocks.

13. The method of claim 1 wherein said receiver comprises a rover GNSS receiver, which method includes the additional steps of:

providing a base receiver unit with a base GNSS receiver and a base RF transmitter;

providing a rover receiver unit with said rover GNSS receiver and a rover RF receiver;

transmitting real-time kinematic (RTK) carrier phase correction signals from said base RF transmitter to said rover RF receiver; and

said processor using said RTK correction signals for deriving a position and attitude solution for said structure.

14. The method of claim 13 wherein said receivers comprise L1-only (single frequency) receivers, which method includes the additional steps of:

transmitting code and carrier phase data from said base RF transmitter to said rover RF receiver;

with the rover receiver unit, determining the relative locations and the relative ambiguities of the multiple antennas using said distance, geometry and clock constraints in an attitude and position solution;

storing said attitude and position solution;

storing current GNSS carrier phase observations;

time-tag matching said stored attitude and position solution and said GNSS carrier phase observations with data from the base receiver unit to avoid extrapolation errors; and

forming single or double difference equations and solving for the global ambiguities using said relative antenna attitudes and positions.

15. The method of claim 1 wherein said receiver comprises a rover receiver on said structure, which method includes the additional steps of:

providing a base receiver;

providing a base antenna connected to said base receiver;

providing multiple rover antennas connected to said rover receiver and mounted on said structure;

constraining said antennas by distance and geometry with respect to each other and said structure;

sharing or synchronizing a clock signal between said receivers; and

computing a position solution for said structure with at least one of said rover antennas being partially blocked.

16. The method of claim 15, which includes the additional steps of:

providing a base receiver unit including said base receiver, said base antenna and a base processor;

providing a rover receiver unit including said rover receiver, said rover antennas and said rover processor;

providing an orientation device mounted on said structure; and

said rover processor using a GNSS-derived position solution for said structure and an orientation of said structure from said orientation device for determining a position and heading solution.

17. The method of claim 1, wherein said structure comprises a fixed or slow-moving structure and said receiver comprises a master receiver, which method includes the additional steps of:

providing a slave receiver;

locating multiple slave antennas on said structure with a satellite-blocking portion of said structure located between said slave antennas;

connecting said slave antennas to said slave receiver;

constraining said slave antennas by distance and geometry with respect to each other and said structure;

providing an antenna input switch connected to said antennas;

connecting said antenna input switch to a receiver input;

switching the receiver input among said antennas with said antenna input switch;

sharing or synchronizing a clock signal between said receivers;

computing a position solution for said structure with at least one of said slave antennas being partially blocked;

providing said slave receiver with a temperature sensor connected to said slave processor;

providing a thermocouple connected to said temperature sensor; and

programming said slave processor with a temperature look-up table to compensate for ambient temperature at said slave antennas with input from said thermocouple and said temperature sensor.

3. The method of claim I Wherein said structure comprises a marine vessel, a terrestrial vehicle or an aircraft, which method includes the additional steps of:

mounting said antennas along a transverse or longitudinal axis of said vehicle.

4. The method of claim 3 wherein said structure comprises a vehicle with a windshield, a rear window and a roof and said receiver comprises a first receiver, which method includes the additional steps of:

providing a second receiver connected to said processor;

mounting a first antenna inside said vehicle in proximity to one of said vehicle windshield and rear window;

connecting said first antenna to said first receiver;

mounting a second antenna inside said vehicle in proximity to the other of said windshield and said rear window;

connecting said second antenna to said second receiver;

providing a common clock signal to said receivers for processing GNSS measurement signals thereat in unison; and

partially blocking a view of satellites with said automobile whereby each antenna receives measurements from a different subset of the available satellites.

5. The method of claim 3 wherein said structure comprises an aircraft with a fuselage and said receiver comprises a master receiver, which method includes the additional steps of:

providing a master antenna mounted on top of the aircraft fuselage and connected to said master receiver;

providing a slave receiver;

providing first and second slave antennas mounted on opposite sides of said fuselage and connected to said slave receiver;

said aircraft in a banking attitude blocking the slave antennas from one or more GNSS satellites;

providing an antenna input switch connected to said slave antennas;

connecting said antenna input switch to a slave receiver input; and

switching the receiver input among said antennas with said antenna input switch.

18. A GNSS method of determining an earth-referenced attitude and position of a structure, which method comprises the steps of:

providing master and slave GNSS receivers on said structure;

providing master and slave GNSS antennas connected to said master and slave GNSS receivers respectively;

mounting said antennas on said structure;

constraining said antennas relative to said structure and each other based on fixed distance and geometry constraints;

receiving different GNSS signal multipath effects at respective different antenna locations;

at least one of said antennas being at least partially blocked from a GNSS satellite constellation by said structure,

providing a processor connected to said receivers;

said processor processing inputs from said GNSS antennas for determining an earth-referenced attitude and position of said structure; and

said processor averaging said different GNSS signal multipath effects and thereby reducing or eliminating multipath errors from said GNSS-defined position of said structure.

19. The method according to claim 18, which includes the additional steps of:

providing an orientation device mounted on said structure;

said antennas receiving measurements from four unique satellites;

sharing or synchronizing a clock signal between said receivers; and

said processor processing inputs from said orientation device, said common clock signal and said GNSS antennas for determining an earth-referenced attitude and position of said structure.

20. The method according to claim 18, which includes the additional steps of:

providing an orientation device mounted on said structure;

said antennas receiving measurements from four unique satellites;

at least one of said satellites providing measurement signals to at least two antennas; and

said antennas collectively receiving at least five measurement signals; and

said processor processing inputs from said orientation device and said GNSS antennas for determining an earth-referenced attitude and position of said structure.

21. The method according to claim 18, which includes the additional steps of:

said antennas receiving measurements from four unique satellites;

at least two of said satellites each providing measurement signals to at least two of said antennas;

said antennas collectively receiving at least six measurement signals; and

said processor processing inputs from said GNSS antennas for determining an earth-referenced attitude and position of said structure.

22. A GNSS system for determining an earth-referenced attitude and position of a structure, which system includes:

a GNSS receiver;

multiple GNSS antennas connected to said receiver;

said antennas being mounted on said structure and constrained relative to said structure and each other based on fixed distance and geometry constraints;

said antennas being positioned for receiving different GNSS signal multipath effects at their respective different antenna locations;

a processor connected to said receiver;

said processor processing said GNSS antenna inputs for determining an earth-referenced attitude and position of said structure; and

said processor averaging said different GNSS signal multipath effects and thereby reducing or eliminating multipath errors from said GNSS-defined position of said structure.