Removing biases in dual frequency GNSS receivers using SBAS

• US 8,085,196 B2
• Filed: 03/11/2009
• Issued: 12/27/2011
• Est. Priority Date: 03/11/2009
• Status: Active Grant

• Current Assignee: Hemisphere GNSS(USA) Incorporated
• Original Assignee: Hemisphere GPS LLC (Kubota Corporation)
• Inventors: Whitehead, Michael L.
• Primary Examiner(s): Phan, Dao
• Application Number:
  US12/401,948
• Publication Number:
  US 20100231443A1
• Time in Patent Office: 1,021 Days
• Field of Search: 342/357.23, 342/357.44, 342/357.46, 342/357.62, 701/213, 701/215
• US Class Current: 342/357.44
• CPC Class Codes: G01S 19/072 Ionosphere corrections
• CPC Class Codes: G01S 19/32 Multimode operation in a single same satellite system, e.g. GPS L1/L2
• CPC Class Codes: G01S 19/40 Correcting position, velocity or attitude

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).

Claims

1. A GNSS receiver system for receiving signals from GNSS satellites, including at least one SBAS satellite, which receiver system includes:

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

an ionosphere-free pseudo range being SBAS-corrected using data broadcast in the SBAS signal as well as data in the bias correction table according to the formula;

2. The GNSS receiver system of claim 1, which includes:

a Kalman filter adapted for estimating the troposphere as its state.

3. The system of claim 1, which includes:

said GNSS receiver comprising a dual frequency receiver using one of;

L2(P) and L1(P); and

L2(P) and L1(C/A).

4. The system of claim 1, which includes means for calibrating the biases using either:

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.

5. The method of claim 1, which includes means for providing a separate B_TOTAL value for each of multiple GNSS satellites.

6. A GNSS receiver system for receiving pseudo range signals from GNSS satellites, including at least one SBAS satellite, which receiver system includes:

a receiver including a nonvolatile memory adapted for storing a table of bias corrections for at least one GNSS satellite;

a microprocessor controller connected to said GNSS receiver;

each bias correction including at least one of a group delay correction component and an inter-signal bias correction component;

the pseudo range signals being bias-corrected using data broadcast in the SBAS signal as well as data in the bias correction table; and

the pseudo range being SBAS-corrected using a GNSS broadcast clock model and a broadcast group delay, each satellite sending respective satellite-specific correction values and the biases being calibrated 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.