AUTOMATIC DETECTION OF GPS SA BASE VALUE FOR HFOM

• US 20070024495A1
• Filed: 07/29/2005
• Published: 02/01/2007
• Est. Priority Date: 07/29/2005
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Johnson, Steve, Conner, Kevin
• Granted Patent: US 7,570,205 B2
• Time in Patent Office: Days
• US Class Current: 342/357.250
• CPC Class Codes: G01S 19/13 Receivers
• CPC Class Codes: G01S 19/42 Determining position

Abstract

An apparatus and method for detecting the type of Selective Availability (SA) engine in a Global Positioning System (GPS) receiver. The apparatus reverse computes a User Equivalent Range Error (UERE) value and filters it. The filtered value is run through a hysteresis to determine the GPS engine type. The engine type determination is used to adjust values used by other systems.

Claims

1. A method for automatically determining a selective availability engine type of a Global Positioning System (GPS) receiver, the method comprising:

receiving signals at a GPS receiver having a selective availability engine;

determining the type of the selective availability engine based on the received signals; and

adjusting at least one value based on the engine type determination.

2. The method of claim 1, wherein the at least one value includes a horizontal figure of merit (HFOM) limit.

3. The method of claim 1, further comprising determining at least one Horizontal Figure of Merit (HFOM) value and at least one Horizontal Dilution of Precision (HDOP) value.

4. The method of claim 3, wherein determining further comprises:

computing an estimate of User Equivalent Range Error (UERE) based on the HFOM and the HDOP values;

filtering the UERE estimate; and

determining the engine type based on the filtered UERE.

5. The method of claim 4, wherein filtering includes a hysteresis analysis.

6. An apparatus for automatically determining a selective availability engine type of a Global Positioning System (GPS) receiver, the apparatus comprising:

a means for receiving signals at a GPS receiver having a selective availability engine;

a means for determining the type of the selective availability engine based on the received signals; and

a means for adjusting at least one value based on the engine type determination.

7. The apparatus of claim 6, wherein the at least one value includes a Horizontal Figure of Merit (HFOM) limit.

8. The apparatus of claim 6, further comprising a means for determining at least one Horizontal Figure of Merit (HFOM) value and at least one Horizontal Dilution of Precision (HDOP) value.

9. The apparatus of claim 8, wherein determining further comprises:

a means for computing an estimate of User Equivalent Range Error (UERE) based on the HFOM and the HDOP values;

a means for filtering the UERE estimate; and

a means for determining the selective availability engine type based on the filtered UERE.

10. The apparatus of claim 9, wherein the means for filtering includes a hysteresis analysis.

11. An apparatus for automatically determining a Selective Availability (SA) engine type of a Global Positioning System (GPS) receiver, the apparatus comprising:

a receiver configured to receive signals from at least one GPS satellite;

a SA engine configured to set at least one value based on a predefined SA engine type; and

a detector configured to determine the SA type of the engine based on the received signals.

12. The apparatus of claim 11, further comprising a component configured to set at least one value based on the engine type determination, wherein the at least one value includes a Horizontal Figure of Merit (HFOM) limit.

13. The apparatus of claim 11, wherein the received signals include a Horizontal Figure of Merit (HFOM) value and a Horizontal Dilution of Precision (HDOP) value.

14. The apparatus of claim 13, wherein the detector comprises:

a first component configured to compute an estimate of User Equivalent Range Error (UERE) based on the HFOM and the HDOP values;

a second component configured to filter the UERE estimate; and

a third component configured to determine the SA engine type based on the filtered UERE.

15. The apparatus of claim 14, wherein the second component filters based on a hysteresis analysis.

16. The apparatus of claim 11, wherein the receiver and detector are mounted in an aircraft.