PHASE BASED MEASUREMENT CORRECTIONS

• US 20100166044A1
• Filed: 12/17/2007
• Published: 07/01/2010
• Est. Priority Date: 12/19/2006
• Status: Active Grant

• Current Assignee: Qinetiq Limited (QinetiQ Group PLC)
• Original Assignee: Qinetiq Limited (QinetiQ Group PLC)
• Inventors: Offer, Charles Robert
• Granted Patent: US 8,451,880 B2
• Time in Patent Office: Days
• US Class Current: 375/148
• CPC Class Codes: G01S 19/04 providing carrier phase data
• CPC Class Codes: G01S 19/072 Ionosphere corrections
• CPC Class Codes: G01S 19/41 Differential correction, e.g. DGPS [differential GPS]
• CPC Class Codes: G01S 19/44 Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method

Abstract

A method for providing correction values for phase based measurements. Where averaging techniques are employed for exploiting redundancy in multiple measurements, by constraining the phase ambiguity in a correction value to be an integer multiple of the carrier wavelength, carrier phase based measurements can be used.

Claims

1. A method for deriving a correction value A_n for a phase-based satellite navigation measurement for a satellite n, from a common set of a plurality of base station reference receivers M and a plurality of satellites N, wherein the phase ambiguity a_n in the correction value is constrained to be an integer multiple of the carrier wavelength λ

.

2. The method of claim 1, wherein component correction values A′

are averaged over all base station receivers and all satellites in the common set, and wherein double differenced ambiguities δ

a are subtracted from each component correction value prior to averaging.

3. The method of claim 1 or claim 2, comprising:

For each base station reference receiver, establishing a component correction value A′

for each of a set of satellite measurements, subtracting double differenced ambiguities δ

a from each of said component values and averaging over all satellites in the set to produce a first intermediate value,

For each base station reference receiver, establishing a component correction value A′

_n for measurement for said satellite n, subtracting the double differenced ambiguity corresponding to said base station and said satellite n, and subtracting said first intermediate value to produce a second intermediate value; and

Averaging said second value over each base station in a set, to produce a final correction value A_n.

4. A method according to claim 2 or claim 3, wherein said double differenced ambiguities δ

a are offset by an integer multiple of the carrier wavelength c_n.

5. A method according to claim 4, wherein said double differenced ambiguities are determined relative to a chosen satellite-receiver reference pair p₀q₀, and wherein the phase ambiguity a_n in the correction value is equal to the ambiguity for said chosen reference receiver q₀, offset by constant c_n.

6. A method according to claim 5, wherein said constant c_n is adjusted to compensate for a change of reference pair p₀q₀.

7. A method according to claim 6, wherein if said reference pair p₀q₀ is changed to reference pair p₁q₁, then c_n is incremented by the double differenced ambiguity for said previous reference receiver q₀ determined relative to satellite-receiver reference pair p₁q₁.

8. A method according to any preceding claim, wherein said phase correction value is determined as:

9. A method according to any preceding claim, wherein said correction value is used to determine an estimate of position of an object relative to an average of the positions of the base station receivers, and wherein said estimate is subsequently transformed to be relative to a selected base station reference point.

10. A method of deriving a satellite navigation estimate for an object relative to a plurality of base station reference receivers, the method comprising:

deriving a first estimate of the position of said object relative to an average position of said reference receivers, and

deriving a second estimate of position of said object relative to a selected base station reference point, based on said first estimate.

11. A method according to claim 10, wherein said average position of the reference receivers is determined by the physical arrangement of said receivers.

12. A method according to claim 10 or claim 11, wherein said estimate of position is derived from phase-based satellite measurements

13. A method according to any one of claims 10 to 12, wherein deriving said first estimate includes ambiguity fixing.

14. A method according to any one of claims 10 to 13, wherein deriving said first estimate includes deriving satellite measurement correction values.

15. A method according to claim 14, wherein in deriving each correction value, the phase ambiguity is constrained to be an integer multiple of the carrier wavelength λ

.

16. A method for deriving a correction value A_n for a phase-based measurement of separation of a transmission source n, from a common set of a plurality of reference stations M, where the reference stations each make phase based measurements of distance from a plurality of transmission sources N, wherein the phase ambiguity a_n in the correction value is constrained to be an integer multiple of the carrier wavelength λ

.