Detection and correction of anomalous measurements and ambiguity resolution in a global navigation satellite system receiver

Patent metadata

Field	Value
Publication number	US-9891325-B2
Application number	US-201414273120-A
Country	US
Kind code	B2
Filing date	May 8, 2014
Priority date	Nov 17, 2009
Publication date	Feb 13, 2018
Grant date	Feb 13, 2018

Abstract

A global navigation system includes a first navigation receiver located in a rover and a second navigation receiver located in a base station. Single differences of measurements of satellite signals received at the two receivers are calculated and compared to single differences derived from an observation model. Anomalous measurements are detected and removed prior to performing computations for determining the output position of the rover and resolving integer ambiguities. Detection criteria are based on the residuals between the calculated and the derived single differences. For resolving integer ambiguities, computations based on Cholesky information Kalman filters and Householder transformations are advantageously applied. Changes in the state of the satellite constellation from one epoch to another are included in the computations.

First claim

The invention claimed is:

1. A method for processing measurements in a global navigation satellite system comprising a first navigation receiver located in a rover and a second navigation receiver located in a base station, the method comprising the steps of:
receiving a first plurality of measurements based on a first plurality of carrier signals received by the first navigation receiver from a plurality of global navigation satellites;
receiving a second plurality of measurements based on a second plurality of carrier signals received by the second navigation receiver from the plurality of global navigation satellites, each carrier signal in the second plurality of carrier signals corresponding to a carrier signal in the first plurality of carrier signals, and each measurement in the second plurality of measurements corresponding to a measurement in the first plurality of measurements;
calculating a first plurality of single differences based on the first plurality of measurements and the second plurality of measurements;
determining a state vector based on a prescribed function using the first plurality of single differences, wherein the prescribed function is a Gauss-Newton method;
calculating a second plurality of single differences based on an observation model represented by a prescribed mathematical model applicable to raw measurements for the global navigation satellite system, wherein the prescribed mathematical model is given by:
ρ r,k f,s =R r,k f,s +c (τ r,k +δτ r,k (ρ)f,s −τ k s )+ T r,k s +μ f/f ref ,s I r,k f ref ,s +ζ r,k (ρ)f,s

and
φ r,k f,s =R r,k f,s +c (τ r,k +δτ r,k (φ)f,s −τ k s )+ T r,k s +μ f/f ref ,s I r,k f ref ,s +λ f,s ( M r f,s +ψ r,k s )+ζ r,k (φ)f,s ;

where:
The set of index numbers r,k f,s refer to the following:
f is the index number of the frequency band,
s is the index number of a satellite,
r is the index number of a receiver,
k is the index number of a system time instant,

ρ r,k f,s are line-of-sight pseudo-ranges (in meters) between satellite s and receiver r,
φ r,k f,s are line-of-sight carrier phase measurements (in meters) between satellite s and receiver r,
c is the speed of light (2.99792458×10 8 m/s),
R r,k f,s =R(r r,k s +b r,k f,s ,r r,k s +c r,k f,s ) is the distance from the phase center of the transmitting antenna on satellite s to the phase center of the receiving antenna on receiver r,
r=(x, y, z) T is the position vector, also referred to herein as the radius vector, in the World Geodetic System 84 (WGS 84) coordinate frame referenced to the center of the Earth,
r r,k s is the radius vector of satellite s at the instant that the satellite signal is received at receiver r,
b r,k f,s is the displacement vector of the phase center (for the frequency band f) of the receiving antenna on the receiver r relative to the antenna reference point; this vector depends on the direction of satellite s,
c r,k f,s is the displacement vector of the phase center (for the frequency band f) of the transmitting antenna on the satellite s relative to the center-of-mass of the satellite,
λ f,s is the wavelength of the carrier signal transmitted by satellite s on frequency band f,
τ k s and τ r,k are the clock offsets of the satellite clock and the receiver clock, respectively, relative to the system time,
δτ r,k (ρ)f,s and δτ r,k (φ)f,s are the code-measurement channel delay and phase-measurement channel delay, respectively,
T r,k s is the troposphere delay,
I r,k fref,s is the ionosphere delay caused by propagation of the satellite signal through the ionosphere,

μ

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is the ionosphere frequency ratio, where f ref is the index number of a reference frequency band,
ψ r,k s =ψ r,k (⊥),s +ψ r,k (∥),s is the phase incursion (phase increment) due to change in mutual orientation of the antenna on satellite s and the antenna on receiver r. It includes a linear increment ψ r,k (⊥),s caused by turning the antennas in the plane of their dipole axes, and a nonlinear increment ψ r,k (∥),s caused by mutual deviation of axes normal to antenna dipoles from the line of sight,
ζ r,k (ρ)f,s and ζ r,k (φ)f,s are code noise error (including DLL errors and multipath errors) and phase noise error (including PLL errors and multipath errors), respectively,

calculating a plurality of residuals based on the first plurality of single differences and the second plurality of single differences;
determining whether the first plurality of measurements and the second plurality of measurements are consistent with the observation model; and
in response to determining that the first plurality of measurements and the second plurality of measurements are not consistent with the observation model, detecting anomalous measurements; and
eliminating the detected anomalous measurements;
determining whether the remaining measurements are sufficient for determining the state vector, and if the remaining measurements are sufficient for the determining of the state vector then
calculating a position of the rover based on the remaining measurements.

2. The method of claim 1 , wherein the step of determining whether the first plurality of measurements and the second plurality of measurements are consistent with the observation model comprises the steps of:
calculating the absolute value of each residual in the plurality of residuals;
comparing the absolute value of each residual in the plurality of residuals to a threshold value;
determining that the first plurality of measurements and the second plurality of measurements are consist

Assignees

• Topcon Positioning Systems Inc

Inventors

• Milyutin Daniel
• Plenkin Andrey

Classifications

• G01S19/43 Primary

  using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry · CPC title

• G01S19/20 Primary

  Integrity monitoring, fault detection or fault isolation of space segment · CPC title

• G01S19/44

  Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method · CPC title