REMOVING BIASES IN DUAL FREQUENCY GNSS RECEIVERS USING SBAS
First Claim
1. A method of determining the location of a global navigation satellite system (GNSS) receiver including a receiver memory, which method includes the steps of:
- computing ionosphere-free pseudo ranges using code and carrier phases of GNSS signals;
correcting said ionosphere-free pseudo ranges using satellite-based augmentation system (SBAS) clock and orbit corrections;
providing a microprocessor controller connected to said GNSS receiver;
computing a table of biases to further correct said pseudo ranges;
uploading into said receiver memory biases; and
computing locations of said receiver using said corrected pseudo ranges and said biases.
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Accused Products
Abstract
A method for removing biases in dual frequency GNSS receivers circumvents the need for ionosphere corrections by using L2(P) in combination with either L1(P) or L1(C/A) to form ionosphere-free ranges. A table of biases is stored in microprocessor controller memory and utilized for computing a location using corrected ionosphere-free pseudo ranges. A system for removing biases in dual frequency GNSS receivers includes a dual frequency GNSS receiver and a controller microprocessor adapted to store a table of bias values for correcting pseudo ranges determined using L2(P) in combination with either L1(P) or L1(C/A).
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Citations
18 Claims
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1. A method of determining the location of a global navigation satellite system (GNSS) receiver including a receiver memory, which method includes the steps of:
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computing ionosphere-free pseudo ranges using code and carrier phases of GNSS signals; correcting said ionosphere-free pseudo ranges using satellite-based augmentation system (SBAS) clock and orbit corrections; providing a microprocessor controller connected to said GNSS receiver; computing a table of biases to further correct said pseudo ranges; uploading into said receiver memory biases; and computing locations of said receiver using said corrected pseudo ranges and said biases. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of determining the location of a global navigation satellite system (GNSS) receiver, which method includes the steps of:
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computing ionosphere-free pseudo ranges using code and carrier phases of GNSS signals; correcting said ionosphere-free pseudo ranges using satellite-based augmentation system (SBAS) clock and orbit corrections; providing a microprocessor controller connected to said GNSS receiver; storing in said microprocessor controller a table of pseudo range correction biases; correcting said computed pseudo ranges using said biases; carrier-smoothing said pseudo ranges at a smoothing interval of greater than one half hour; estimating the troposphere as the state of a Kalman filter; using either;
L2(P) and L1(P);
or L2(P) and L1(C/A);said GNSS receiver comprising a dual frequency receiver; correcting the L1(C/A) pseudo range according to the formula
[R−
(TSV−
τ
GD)−
ISCL1/CA]+TSVGPS+[TSV−
TSVGPS+ISCL1/CA−
(τ
GD−
τ
GDGPS)]=Rwherein; the GPS broadcast clock model=TSVGPS; the broadcast group-delay=τ
GDGPS;the superscript “
GPS”
indicates that TSVGPS and τ
GDGPS are estimates provided by the GPS Control Segment rather than the true values;the GPS navigation message, which is modulated on the GPS transmitted signals, contains coefficients of a time-based polynomial fitting TSVGPS; the navigation message contains a single word providing the group-delay, τ
GDGPS;each satellite sends its respective, satellite-specific values for the above quantities; and the SBAS clock correction, TSBAS, can be broken down into its individual constituents as follows;
TSBAS=TSV−
TSVGPS+ISCL1/CA−
(τ
GD−
τ
GDGPS)
Piono— free— correctedCA=K1C1−
K2P2+TSVGPS+TSBASBISC— TGD
BISC— TGDK2ISCL1/CA+(τ
GD−
τ
GDGPS); and
Piono— free— corrected=Rcalibrating the biases using a Kalman filter or a least squares method to;
estimate and remove the effects of un-modeled troposphere errors and clock errors; and
to effectively time-average the data; andproviding a separate BTOTAL value for each of multiple GNSS satellites.
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11. A GNSS receiver system for receiving signals from GNSS satellites, including at least one SBAS satellite, which receiver system includes:
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a receiver including a nonvolatile memory adapted for storing a table of bias corrections for at least one GNSS satellite; each bias correction including at least one of a group delay correction component and an inter-signal bias correction component; and means to compute an ionosphere-free pseudo range using data broadcast in the SBAS signal as well as data in the bias correction table. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A storage medium encoded with a machine-readable computer program code, the code including instructions for determining the location of a GNSS receiver, which method comprises the steps of:
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computing ionosphere-free pseudo ranges using code and carrier phases of GNSS signals; correcting said ionosphere-free pseudo ranges using satellite-based augmentation system (SBAS) clock and orbit corrections; providing a microprocessor controller connected to said GNSS receiver; storing in said microprocessor controller a table of pseudo range correction biases; and correcting said computed pseudo ranges using said biases.
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18. A computer data signal comprising code configured to cause a processor to implement a method for determining the location of a GNSS receiver, which method comprises the steps of:
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computing ionosphere-free pseudo ranges using code and carrier phases of GNSS signals; correcting said ionosphere-free pseudo ranges using satellite-based augmentation system (SBAS) clock and orbit corrections; providing a microprocessor controller connected to said GNSS receiver; storing in said microprocessor controller a table of pseudo range correction biases; and correcting said computed pseudo ranges using said biases.
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Specification