METHOD FOR ACCURACY ESTIMATION OF NETWORK BASED CORRECTIONS FOR A SATELLITE-AIDED POSITIONING SYSTEM

• US 20100207817A1
• Filed: 08/22/2008
• Published: 08/19/2010
• Est. Priority Date: 09/18/2007
• Status: Active Grant

• Current Assignee: Leica Geosystems AG (Hexagon AB)
• Original Assignee: Leica Geosystems AG (Hexagon AB)
• Inventors: Brown, Neil
• Granted Patent: US 8,072,373 B2
• Time in Patent Office: Days
• US Class Current: 342/357.440
• CPC Class Codes: G01S 19/04 providing carrier phase data
• CPC Class Codes: G01S 19/074 providing integrity data, e.g. WAAS

Abstract

In a method for accuracy estimation of network based corrections for a satellite-aided positioning system, with a network of reference stations code and phase measurements are recorded by the reference stations and transferred to a network processing centre. The measurements are converted to observables and single-differences between a master station and at least one auxiliary station selected for each reference station are calculated. Estimates of single-difference between each reference station and the corresponding master station are generated and slant residuals for each reference station and satellite are calculated by using the difference between calculated single-differences and estimates. Subsequently double-differences are formed by differencing satellite s and the slant residuals of a reference satellite k, leading to zenith residuals calculated by mapping the double-differences to a zenith value. Error values for each reference station are computed by using the zenith residuals and residual dispersive and non-dispersive error values for a potential rover position are estimated by combining residual dispersive and non-dispersive error values of all reference stations. The accuracy of network based corrections is represented graphically by generating a map as a grid of potential rover positions with estimated residual dispersive and non-dispersive error values.

Claims

1-13. -13. (canceled)

14. A method for accuracy estimation with continuous representation of network based corrections for a satellite-aided positioning system, with a network of reference stations for receiving signals transmitted by satellites of the positioning system and transmitting corrections to a rover, wherein the method comprises:

recording code and phase measurements by the reference stations;

transferring the measurements to a network processing center;

converting the measurements to dispersive and/or non-dispersive observables;

correcting the measurements for the geometric range, ambiguity, antenna phase centre variations, tropospheric path delays using a standard atmosphere model and clock error;

calculating single-differences between a master station and at least one auxiliary station selected for each reference station;

generating estimates of single-difference between each reference station and the corresponding master station;

calculating slant residuals for each reference station and satellite by using the difference between calculated single-differences and estimates;

forming double-differences by differencing between the slant residuals for each satellite s and the slant residuals of a reference satellite k;

calculating zenith residuals by mapping the double-differences to the zenith direction;

computing dispersive and/or non-dispersive error values for each reference station by using the zenith residuals; and

estimating the residual dispersive and/or non-dispersive error values for a potential or actual rover position after the network corrections have been applied by combining dispersive and/or non-dispersive error values of all reference stations.

15. The method according to claim 14, wherein the single-differences are calculated for each reference station between a master station and a set of nearby reference stations as auxiliary stations.

16. The method in claim 14, wherein the interpolating uses a linear combination model, distance-based linear interpolation method, linear interpolation method, low-order surface model or least squares collocation.

17. The method according to claim 14, wherein the non-dispersive error values for a potential or actual rover position are estimated by using a digital elevation model which provides the height information for the potential rover position.

18. The method according to claim 14, wherein the slant residuals are calculated according to

Δ

ν

_dispersive=Δ

{tilde over (Φ

)}_dispersive−

Δ

{circumflex over (Φ

)}_dispersive

Δ

ν

_{non-dispersive}=Δ

{tilde over (Φ

)}_{non-dispersive}−

Δ

{circumflex over (Φ

)}_{non-dispersive}

where ν

is the slant residual, Δ

is a single difference operator, Φ

is a corrected code or ambiguity leveled phase range and {circumflex over (Φ

)} is an estimated code or ambiguity leveled phase range.

19. The method according to claim 18 wherein the double-differenced slant residuals are formed according to

∇

Δ

ν

_dispersive=Δ

ν

_dispersive^s−

Δ

ν

_dispersive^k

∇

Δ

ν

_{non-dispersive}=Δ

ν

_{non-dispersive}^s−

Δ

ν

_{non-dispersive}^k

where ∇

Δ

is the double difference operator.

20. The method according to claim 19, wherein the zenith residuals z_dispersive and/or z_{non-dispersive} are calculated with the mapping function z_dispersive=∇

Δ

ν

_dispersive·

sin(θ

) and z_{non-dispersive}=∇

Δ

ν

_{non-dispersive}·

sin(θ

) where θ

is the satellite elevation in radians.

21. The method according to claim 20, wherein the residual dispersive error values I_r and/or non-dispersive error values T_r are computed for each reference station r using the double difference zenith residuals

22. The method according to claim 21, wherein the residual dispersive error value I_φ

,λ

for a potential or actual rover position at a defined latitude and longitude φ

,λ

is estimated as

23. The method according to claim 21, wherein the residual non-dispersive error value T_φ

,λ

, h for a potential or actual rover position at a defined latitude, longitude and height φ

,λ

,h is estimated as

24. A method for graphically representing the accuracy of network based corrections with generating a map by estimating error values for a grid of potential rover positions with the method according to the method of claim 14.

25. A method for recording and/or communicating accuracy estimates of network based corrections for individual rovers by estimating error values for the rover'"'"'s positions with the method according to the method of claim 14.

26. A computer program product as a recording on a tangible data medium with code sequences for carrying out the method according to claim 14.

27. The method according to claim 14, wherein the network includes an RTK network.

28. The method according to claim 14, wherein generating estimates of single-difference between each reference station and the corresponding master station is accomplished by interpolating single difference values between the master station and the corresponding auxiliary stations.