Ionosphere modeling apparatus and methods
First Claim
Patent Images
1. A method of processing a set of GNSS signal data derived from signals having at least two carrier frequencies and received from two or more satellites at two or more reference stations over multiple epochs, comprising:
- a. For each satellite, forming a geometry-free combination of GNSS signal data derived from two carrier frequencies received at the reference stations during an epoch;
b. For each satellite, applying a filter to the geometry-free combination to obtain state values representing (i) a carrier-phase ambiguity for each reference station and (ii) ionospheric advance at a reference point and state values representing variation of ionospheric advance relative to the reference point across a network area, along with error estimates for the state values; and
c. Repeating a, and b, for each of multiple epochs to update the state values and error estimates.
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Abstract
Methods and apparatus which characterize the ionospheric error across a network of GNSS reference stations are presented. The method relies on dual-frequency phase measurements in a geometry-free linear combination. The data are filtered for ambiguities and the characteristic parameters of the ionosphere. In combination with filter results from other combinations of phase measurements (ionosphere free combination), the physically-based model provides rapid and reliable ambiguity resolution.
50 Citations
22 Claims
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1. A method of processing a set of GNSS signal data derived from signals having at least two carrier frequencies and received from two or more satellites at two or more reference stations over multiple epochs, comprising:
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a. For each satellite, forming a geometry-free combination of GNSS signal data derived from two carrier frequencies received at the reference stations during an epoch; b. For each satellite, applying a filter to the geometry-free combination to obtain state values representing (i) a carrier-phase ambiguity for each reference station and (ii) ionospheric advance at a reference point and state values representing variation of ionospheric advance relative to the reference point across a network area, along with error estimates for the state values; and c. Repeating a, and b, for each of multiple epochs to update the state values and error estimates. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. Apparatus for processing a set of GNSS signal data derived from signals having at least two carrier frequencies and received from two or more satellites at two or more reference stations over multiple epochs, comprising:
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a. A processing element to prepare a geometry-free combination of GNSS signal data derived from two carrier frequencies received at the reference stations during an epoch; and b. For each satellite, a filter to obtain from the geometry-free combination state values representing (i) a carrier-phase ambiguity for each reference station and (ii) ionospheric advance at a reference point and variation of ionospheric advance relative to the reference point across a network area, along with error estimates for the state values, wherein the processing element a, and the filter b, are operative over each of multiple epochs to update the state values and error estimates. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A network correction data stream prepared by processing a set of GNSS signal data derived from signals having at least two carrier frequencies and received from two or more satellites at two or more reference stations over multiple epochs, wherein the data stream is prepared by:
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a. For each satellite, forming a geometry-free combination of GNSS signal data derived from two carrier frequencies received at the reference stations during an epoch; b. For each satellite, applying a filter to the geometry-free combination to obtain state values representing (i) a carrier-phase integer ambiguity for each reference station and (ii) ionospheric advance at a reference point and variation of ionospheric advance relative to the reference point across a network area, along with error estimates for the state values; c. Repeating a, and b, for each of multiple epochs to update the state values and error estimates; d. Combining the ambiguity estimates for all carrier phase observations with the set of GNSS signal data to produce a set of network broadcast data for use by GNSS receivers within the network area, and transmitting the network broadcast data for use by GNSS receivers within the network area.
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20. A network correction data stream prepared by processing a set of GNSS signal data derived from signals having at least two carrier frequencies and received from two or more satellites at two or more reference stations over multiple epochs, wherein the data stream is prepared by:
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a. For each satellite, forming a geometry-free combination of GNSS signal data derived from two carrier frequencies received at the reference stations during an epoch; b. For each satellite, applying a filter to the geometry-free combination to obtain state values representing (i) a carrier-phase integer ambiguity for each reference station and (ii) ionospheric advance at a reference point and variation of ionospheric advance relative to the reference point across a network area, along with error estimates for the state values; c. Repeating a, and b, for each of multiple epochs to update the state values and error estimates; d. Forming an ionosphere-free combination of the GNSS signal data; e. Applying a filter to the ionosphere-free geometric combination to obtain state values representing carrier-phase integer ambiguity estimates for the ionosphere-free carrier-phase combination and associated statistical information; f. Combining the state values and associated statistical information of b, and e, to determine ambiguity estimates for all carrier phase observations and associated statistical information; and g. Combining the ambiguity estimates for all carrier phase observations with the set of GNSS signal data to produce a set of network broadcast data for use by GNSS receivers within the network area, and transmitting the network broadcast data for use by GNSS receivers within the network area.
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21. A network correction data stream prepared by processing a set of GNSS signal data derived from signals having at least two carrier frequencies and received from two or more satellites at two or more reference stations over multiple epochs, wherein the data stream is prepared by:
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a. For each satellite, forming a geometry-free combination of GNSS signal data derived from two carrier frequencies received at the reference stations during an epoch; b. For each satellite, applying a filter to the geometry-free combination to obtain state values representing (i) a carrier-phase integer ambiguity for each reference station and (ii) ionospheric advance at a reference point and variation of ionospheric advance relative to the reference point across a network area, along with error estimates for the state values; c. Repeating a, and b, for each of multiple epochs to update the state values and error estimates; d. Forming an ionosphere-free geometric combination of the GNSS signal data; e. Applying a filter to the ionosphere-free combination to obtain state values representing carrier-phase integer ambiguity estimates for the ionosphere-free carrier-phase combination and associated statistical information; f. Applying at least one code filter to the GNSS signal data using a plurality of geometry-free code-carrier combinations to obtain ambiguity estimates for the code-carrier combinations and associated statistical information; g. Combining the state values and associated statistical information of b, e, and f, to determine ambiguity estimates for all carrier phase observations and associated statistical information; and h. Combining the ambiguity estimates for all carrier phase observations with the set of GNSS signal data to produce a set of network broadcast data for use by GNSS receivers within the network area, and transmitting the network broadcast data for use by GNSS receivers within the network area.
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22. A network correction data stream prepared by processing a set of GNSS signal data derived from signals having at least three carrier frequencies and received from two or more satellites at two or more reference stations over multiple epochs, wherein the data stream is prepared by:
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a. For each satellite, forming a geometry-free combination of GNSS signal data derived from two carrier frequencies received at the reference stations during an epoch; b. For each satellite, applying a filter to the geometry-free combination to obtain state values representing (i) a carrier-phase integer ambiguity for each reference station and (ii) ionospheric advance at a reference point and variation of ionospheric advance relative to the reference point across a network area, along with error estimates for the state values; c. Repeating a, and b, for each of multiple epochs to update the state values and error estimates; d. Forming an ionosphere-free geometric combination of the GNSS signal data; e. Applying a filter to the ionosphere-free geometric combination to obtain state values representing carrier-phase integer ambiguity estimates for the ionosphere-free carrier-phase combination and associated statistical information; f. Applying at least one code filter to the GNSS signal data using a plurality of geometry-free code-carrier combinations to obtain ambiguity estimates for the code-carrier combinations and associated statistical information; g. Applying at least one quintessence filter to the GNSS signal data using a plurality of geometry-free and ionosphere-free carrier-phase combinations to obtain ambiguity estimates for the geometry-free and ionosphere-free carrier-phase combinations and associated statistical information; h. Combining the state values and associated statistical information of b, e, f, and g, to determine ambiguity estimates for all carrier phase observations and associated statistical information; and i. Combining the ambiguity estimates for all carrier phase observations with the set of GNSS signal data to produce a set of network broadcast data for use by GNSS receivers within the network area, and transmitting the network broadcast data for use by GNSS receivers within the network area.
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Specification