System and Method for Position Determination Using Low Earth Orbit Satellites

• US 20160109581A1
• Filed: 04/01/2011
• Published: 04/21/2016
• Est. Priority Date: 04/02/2010
• Status: Active Grant

• Current Assignee: SkyBitz, Inc. (Ametek Incorporated)
• Original Assignee: SkyBitz, Inc. (Ametek Incorporated)
• Inventors: Harvey, Michael, Malone, Craig, Shankar, Uday, Walgren, Mike, Young, Corwin Walker
• Granted Patent: US 9,784,848 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01S 19/09 providing processing capability normally carried out by the receiver
• CPC Class Codes: G01S 19/25 involving aiding data received from a cooperating element, e.g. assisted GPS
• CPC Class Codes: G01S 19/252 Employing an initial estimate of location in generating assistance data
• CPC Class Codes: G01S 19/258 relating to the satellite constellation, e.g. almanac, ephemeris data, lists of satellites in view
• CPC Class Codes: G01S 19/42 Determining position
• CPC Class Codes: G01S 19/43 using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry
• CPC Class Codes: G01S 19/46 the supplementary measurement being of a radio-wave signal type
• CPC Class Codes: G01S 5/0036 of measured values, i.e. measurement on mobile and position calculation on base station

Abstract

A system and method for position determination using low earth orbit satellites. A mobile terminal affixed to an asset initiates a collection of global positioning system satellite measurements (e.g., code phase) based on a hardware trigger generated by a low earth orbit satellite modem. Timing information reflective of the time of the hardware trigger pulse is transmitted to an operations center along with the global positioning system satellite measurements to enable the operations center to determine a position of the mobile terminal.

Claims

1. A method for determining a location of a mobile terminal, comprising:

receiving, via a low earth orbit satellite, a communication from a mobile terminal that includes timing information and measurements of a plurality of global positioning system satellite signals;

determining a collection time of said global positioning system satellite measurements using said timing information;

determining the coordinates of said low earth orbit satellite using said determined collection time;

determining a low earth orbit satellite beam footprint based on said determined coordinates;

identifying a set of initial candidate points within said determined low earth orbit satellite beam footprint;

determining a set of candidate position solutions using said set of initial candidate points and said global positioning system satellite measurements; and

determining a location of said mobile terminal based on said determined set of candidate position solutions.

2. The method of claim 1, wherein said identifying comprises identifying using a grid of candidate points covering said low earth orbit satellite beam footprint.

3. The method of claim 1, wherein said global positioning system satellite measurements are code phase measurements.

4. The method of claim 1, further comprising culling said set of candidate position solutions using a slant range from said mobile terminal to said low earth orbit satellite.

5. The method of claim 1, further comprising culling said set of candidate position solutions using altitudes of said set of candidate position solutions.

6. The method of claim 1, further comprising culling said set of candidate position solutions using a root mean square of residual that results from a least square processing method on said set of initial candidate points.

7. A method in a mobile terminal affixed to an asset, comprising:

generating, by a low earth orbit satellite modem in response to a global positioning system measurement collection request, a hardware trigger pulse;

initiating, in response to said generated hardware trigger pulse, a collection of global positioning system measurements; and

transmitting, by said low earth orbit satellite modem, a communication to an operations center that includes said global positioning system measurements and timing information indicative of a time of generation of said hardware trigger pulse, said communication enabling said operations center to determine a position of said mobile terminal.

8. The method of claim 7, wherein said collection of global positioning system measurements are performed by said low earth orbit satellite modem.

9. The method of claim 7, wherein said communication also includes a satellite identifier, a beam identifier, and a propagation time from said mobile terminal to said low earth orbit satellite.

10. The method of claim 7, wherein said communication also includes a rough position estimate and a confidence estimate.

11. The method of claim 7, wherein said global positioning system measurements are code phase measurements.

12. A mobile terminal that enables a remote determination of a location of the mobile terminal, comprising:

a global positioning system engine;

a measurement system that receives assisting information from said global positioning system engine, said assisting information enabling said measurement system to reduce the number of global positioning system satellites that are searched, said measurement system taking measurements from signals produced by each of said reduced number of global positioning system satellites; and

a satellite modem that forwards said measurements to a remote operations center via a low earth orbit satellite modem, said forwarded measurements being used by said remote operations center to calculate a location of the mobile terminal at the time of said measurements.

13. The mobile terminal of claim 12, wherein said assisting information includes almanac information.

14. The mobile terminal of claim 12, wherein said assisting information includes ephemeris information.

15. The method of claim 12, wherein said measurements are code phase measurements.

16. A method in an operation center for determining a location of a mobile terminal, comprising:

receiving a communication from said mobile terminal via a low earth orbit satellite, said communication including a rough position estimate of said mobile terminal and a confidence indicator of said rough position estimate;

determining whether said confidence indicator indicates that said rough position estimate is likely within a pre-defined distance from an actual position of said mobile terminal;

if said confidence indicator indicates that said rough position estimate is likely within said pre-defined distance from said actual position of said mobile terminal, then performing a position calculation using only said rough position estimate as a candidate seed point; and

if said confidence indicator indicates that said rough position estimate is not likely within said pre-defined distance from said actual position of said mobile terminal, then performing a position calculation on a plurality of candidate seed points located in a grid covering an area covered by a beam of said low earth orbit satellite.

17. The method of claim 16, wherein said receiving comprises receiving global positioning system satellite measurements from said mobile terminal.

18. A method in an operation center for determining a location of a mobile terminal, comprising:

receiving a communication from said mobile terminal via a low earth orbit satellite, said communication including a rough position estimate of said mobile terminal, and measurements of a plurality of positioning satellite signals;

determining positions of a plurality of positioning satellites in view of said mobile terminal based on said rough position estimate;

discarding measurements of one or more of said plurality of measurements based on an angle of elevation consideration of one or more positioning satellites relative to said mobile terminal; and

determining a position of said mobile terminal using measurements of said positioning satellites that have not been discarded.

19. The method of claim 18, wherein said receiving comprises receiving global positioning system satellite measurements from said mobile terminal.