GNSS-BASED TRACKING OF FIXED OR SLOW-MOVING STRUCTURES

• US 20100109944A1
• Filed: 01/07/2010
• Published: 05/06/2010
• Est. Priority Date: 03/20/2003
• Status: Active Grant

• Current Assignee: Hemisphere GNSS(USA) Incorporated
• Original Assignee: Hemisphere GPS LLC (Kubota Corporation)
• Inventors: Whitehead, Michael L., Feller, Walter J.
• Granted Patent: US 8,138,970 B2
• Time in Patent Office: Days
• US Class Current: 342/357.250
• CPC Class Codes: G01C 15/00 Surveying instruments or accessories not provided for in groups G01C1/00 - G01C13/00
• 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 19/53 Determining attitude
• CPC Class Codes: G01S 5/0063 of measured values, i.e. measurement on base station and position calculation on mobile
• CPC Class Codes: G05D 1/0206 specially adapted to water vehicles
• CPC Class Codes: G05D 1/0259 using magnetic or electromagnetic means
• 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-based method of tracking the movement of a structure, which method comprises the steps of:

providing a GNSS receiver;

providing an antenna array comprising multiple GNSS antennas each selectively connected to said receiver;

mounting said antennas on the structure at fixed locations relative to each other and said structure;

providing an antenna switch control connected to said antennas;

connecting said antenna switch control to a receiver input;

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

providing a processor connected to said receiver and said antenna switch control;

providing a first set of GNSS signals from said antennas to said processor via said receiver;

computing a corresponding first set of GNSS-based locations of said antennas when connected to said receiver;

storing with said processor said first set of GNSS-based locations of said antennas;

providing a second set of GNSS signals from said antennas to said processor via said receiver;

computing with said processor a corresponding second set of GNSS-based locations of said antennas when connected to said receiver;

comparing with said processor said first and second sets of antenna locations; and

providing an output from said processor representing a location change of at least one of said antennas based on said GNSS-based location comparisons.

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

locating said antenna array on said structure with at least a portion of said antennas being blocked by said structure from receiving signals from at least a portion of the visible satellites in the GNSS constellation; and

using GNSS signals from multiple antennas to compute antenna locations relative to each other based on;

     1) partial GNSS constellation observations; and

     2) known locations of said antennas relative to each other.

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

taking said GNSS signal readings at respective antennas at intervals corresponding to the orbital cycles of said satellites and the Earth'"'"'s rotation; and

said processor averaging said different GNSS signal multipath effects and thereby reducing or eliminating multipath errors from said GNSS-defined antenna locations on said structure.

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

receiving common satellite signals at multiple said antennas; and

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

5. 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.

6. The method of claim 5, which includes additional steps of:

providing said master receiver with an RF transmitter;

providing said slave receiver with an RF receiver;

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

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

7. The method of claim 6 wherein said receivers comprise L1-only (single frequency) receivers, which method includes the additional steps of:

transmitting code and carrier phase data from said master RF transmitter to said slave RF receiver;

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

with the processor, 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.

8. The method of claim 1 wherein said structure comprises a dam and said method includes the additional steps of:

mounting said antenna array along a face of said dam; and

monitoring said antenna locations for movement of a respective antenna relative to another antenna.

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

locating a top row of said antennas along a top of said dam;

locating a medial row of said antennas partway down the face of the dam; and

locating a base row of said antennas along a base of said dam face.

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

locating an antenna on an opposite face of said dam.

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

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

providing a thermocouple connected to said temperature sensor; and

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

12. The method of claim 1 wherein said structure comprises a marine vessel and said method includes the additional step of:

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

13. 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.

14. A GNSS-based method of tracking the relative movement of a fixed or slow-moving structure, which method comprises the steps of:

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

providing a master GNSS antenna connected to said master receiver;

providing a slave receiver unit with a slave GNSS receiver and a slave RF receiver;

providing a slave antenna array comprising multiple GNSS antennas each selectively connected to said slave receiver;

mounting said slave antennas on the structure at fixed locations relative to each other and said structure;

locating said antenna array on said structure with at least a portion of said antennas being blocked by said structure from receiving signals from at least a portion of the satellites in the GNSS constellation;

providing an antenna switch control connected to said slave antennas;

connecting said antenna input switch control to a receiver input;

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

providing a processor connected to said receiver and said antenna switch control;

providing a first set of GNSS signals from said antennas to said processor via said receivers;

transmitting real-time kinematic (RTK) carrier phase correction signals from said master RF transmitter to said slave RF receiver;

with the slave 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;

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

synchronizing a clock signal between said receivers;

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

computing a corresponding first set of GNSS-based locations of said antennas when connected to said receivers;

storing with said processor said first set of GNSS-based locations of said antennas;

providing a second set of GNSS signals from said antennas to said processor via said receivers;

computing with said processor a corresponding second set of GNSS-based locations of said antennas when connected to said receivers;

comparing with said processor said first and second sets of antenna locations;

providing an output from said processor representing a location change of at least one of said antennas based on said GNSS-based location comparisons;

using GNSS signals from multiple antennas to compute antenna locations relative to each other based on;

     1) partial GNSS constellation observations; and

     2) known locations of said antennas relative to each other;

taking said GNSS signal readings at respective antennas at intervals corresponding to the orbital cycles of said satellites and the Earth'"'"'s rotation;

said processor averaging said different GNSS signal multipath effects and thereby reducing or eliminating multipath errors from said GNSS-defined antenna locations on said structure;

receiving common satellite signals at multiple said antennas;

separating each pair of said antennas by a distance greater than the carrier phase wavelength of the GNSS signals;

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.

15. A system for determining a GNSS-defined position of a single point fixedly positioned on a slow-moving, structure including a GNSS signal-blocking obstruction, which system comprises:

master and slave GNSS receivers;

master and slave antennas connected to said master and slave receivers respectively and mounted in fixed relation with known geometry and distances relative to each other and to said single point, said antennas being mounted on opposite sides of said mobile structure below said signal-blocking obstruction;

a common clock or synchronized clocks connected to said receivers for simultaneously processing GNSS signals received by said antennas;

an orientation device mounted on said structure for determining an orientation of said structure; and

computing means for determining the GNSS-defined position of said single point using;

(1) GNSS signals received by said master and slave receivers from said master and slave antennas respectively and input to said computing means, said signal-blocking obstruction blocking GNSS signals from certain satellites from said antennas whereby each antenna receives signals from no more than three satellites and collectively said antennas receive GNSS signals from at least four satellites;

(2) the known relative orientation and fixed distances and geometry of said master and slave antennas relative to each other and to said structure;

(3) the known relative orientation and fixed distances and geometry of said single point relative to said master and slave antennas and to said structure; and

(4) the orientation of said structure based on input from said orientation device.

16. The system of claim 15 wherein said computing means uses a single differencing technique based on said known distance and geometry relation of said master and slave antennas for resolving a carrier phase GNSS signal integer ambiguity.

17. The system of claim 15 wherein said structure comprises a dam and said obstruction comprises a portion of the dam.

18. The system of claim 15 wherein said structure comprises a marine vessel and said obstruction comprises a crane mounted on said vessel.

19. A system for determining a GNSS-defined position of a point fixedly positioned on a fixed or slow-moving, mobile structure including a GNSS signal-blocking obstruction, which system comprises:

master and slave GNSS receivers;

master and slave antennas connected to said master and slave receivers respectively and mounted in fixed relation with known geometry and distances relative to each other and to said single point, said antennas being mounted on opposite sides of said mobile structure below said signal-blocking obstruction;

a common clock or synchronized clocks connected to said receivers for simultaneously processing GNSS signals received by said antennas;

an orientation device mounted on said structure for determining an orientation of said structure; and

computing means for determining the GNSS-defined position of said single point using;

(1) GNSS signals received by said master and slave receivers from said master and slave antennas respectively and input to said computing means, said signal-blocking obstruction blocking GNSS signals from certain satellites from said antennas whereby each antenna receives signals from no more than three satellites and collectively said antennas receive GNSS signals from at least four satellites;

(2) the known relative orientation and fixed distances and geometry of said master and slave antennas relative to each other and to said structure;

(3) the known relative orientation and fixed distances and geometry of said single point relative to said master and slave antennas and to said structure; and

(4) the orientation of said structure based on input from said orientation device.

20. The system of claim 19 wherein said computing means uses a single differencing technique based on said known distance and geometry relation of said master and slave antennas for resolving a carrier phase GNSS signal integer ambiguity.

21. The system of claim 19 wherein said structure comprises a dam and said obstruction comprises a portion of the dam.

22. The system of claim 19 wherein said structure comprises a marine vessel and said obstruction comprises a crane mounted on said vessel.