GNSS signal processing methods and apparatus with scaling of quality measure
First Claim
1. Method of operating a processor having associated data storage and program code enabling the processor to estimate parameters derived from global navigational satellite system (GNSS) signals useful to determine a position, comprisingobtaining observations of a GNSS signal from each of a plurality of GNSS satellites;
- feeding the observations to a filter operated by the processor having a state vector at least comprising a float ambiguity for each received frequency of the GNSS signals, each float ambiguity constituting a real number estimate associated with an integer number of wavelengths of the GNSS signal between a receiver of the GNSS signal and the GNSS satellite from which it is received, and the filter being for estimating a float value for each float ambiguity of the state vector;
assigning integer values to at least a subgroup of the estimated float values to define a plurality of integer ambiguity candidate sets;
selecting a number of candidate sets having a quality measure better than a first threshold;
adapting the quality measures of the candidate sets as a function of the quality measure of a reference candidate set having the best quality measure; and
forming a weighted average of a subset of the selected candidate sets on the basis of the adapted quality measures, wherein at least one of selecting the subset of the selected candidate sets and the weighting of each candidate set in the weighted average is based on the adapted quality measures.
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Abstract
A filter estimates a float value for each float ambiguity of a state vector determined from GNSS signals. Integer values are assigned to at least a subgroup of the estimated float values to define integer ambiguity candidate sets. A quality measure is determined for each of the candidate sets. An expectation value of the candidate set having the best quality measure is determined. An error measure as a ratio of the best quality measure to the expectation value is determined. The quality measures of the candidate sets is adapted as a function of the error measure. A weighted average of a subgroup of the candidate sets on the basis of the adapted quality measures is formed. Ambiguities of the weighted average can be used in subsequent operations to aid in determining a position of the receiver.
33 Citations
47 Claims
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1. Method of operating a processor having associated data storage and program code enabling the processor to estimate parameters derived from global navigational satellite system (GNSS) signals useful to determine a position, comprising
obtaining observations of a GNSS signal from each of a plurality of GNSS satellites; -
feeding the observations to a filter operated by the processor having a state vector at least comprising a float ambiguity for each received frequency of the GNSS signals, each float ambiguity constituting a real number estimate associated with an integer number of wavelengths of the GNSS signal between a receiver of the GNSS signal and the GNSS satellite from which it is received, and the filter being for estimating a float value for each float ambiguity of the state vector; assigning integer values to at least a subgroup of the estimated float values to define a plurality of integer ambiguity candidate sets; selecting a number of candidate sets having a quality measure better than a first threshold; adapting the quality measures of the candidate sets as a function of the quality measure of a reference candidate set having the best quality measure; and forming a weighted average of a subset of the selected candidate sets on the basis of the adapted quality measures, wherein at least one of selecting the subset of the selected candidate sets and the weighting of each candidate set in the weighted average is based on the adapted quality measures. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. Apparatus to estimate parameters derived from global navigational satellite system (GNSS) signals useful to determine a position, comprising:
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a processor having associated data storage and program code enabling the processor to obtain observations of a GNSS signal from each of a plurality of GNSS satellites; operate a filter having a state vector at least comprising a float ambiguity for each received frequency of the GNSS signals, each float ambiguity constituting a real number estimate associated with an integer number of wavelengths of the GNSS signal between a receiver of the GNSS signal and the GNSS satellite from which it is received, and the filter being for estimating a float value for each float ambiguity of the state vector; assign integer values to at least a subgroup of the estimated float values to define a plurality of integer ambiguity candidate sets; select a number of candidate sets having a quality measure better than a first threshold; adapt the quality measures of the candidate sets as a function of the quality measure of a reference candidate set having the best quality measure; and form a weighted average of a subset of the selected candidate sets on the basis of the adapted quality measures, wherein at least one of selecting the subset of the selected candidate sets and the weighting of each candidate set in the weighted average is based on the adapted quality measures. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47)
indicate a convergence of the determination of the state vector at and after the determined instance in time.
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40. Apparatus of claim 37, wherein the program code enables the processor to
estimate an achieved precision of a position of the receiver determined based on the weighted ambiguities; - and
indicate a convergence of the determination of the state vector, if the achieved precision of the position is better than an inclusion threshold.
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41. Apparatus of claim 37, wherein the program code enables the processor to
estimate an achieved precision of a position of the receiver determined based on the weighted ambiguities; - and
indicate a non-convergence of the determination of the state vector, if the achieved precision of the position is worse an exclusion threshold.
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42. Apparatus of claim 24, wherein the program code enables the processor to
obtain observations of the at least one frequency of the GNSS signals from the plurality of GNSS satellites to obtain observations at a plurality of instances in time; -
update the float ambiguities of the state vector over time on the basis of the observations; determine that an interruption in tracking of at least one signal of a satellite occurred; and maintain the float ambiguity of the state vector for the at least one signal for which an interruption in tracking occurred at the value before the interruption in tracking occurred.
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43. Apparatus of claim 42, wherein the program code enables the processor to determine that an interruption in tracking of at least one signal of a satellite occurred if an observation for the at least one signal is not available for at least one of the instances in time.
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44. Apparatus of claim 42, wherein the program code enables the processor to determine that an interruption in tracking of at least one signal of a satellite occurred, if a cycle slip occurred.
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45. Apparatus of claim 42, wherein the program code enables the processor to, if, after an interruption in tracking of a signal, tracking of the signal resumes, maintain the float ambiguity of the state vector for the signal for which an interruption in tracking occurred at the value before the interruption in tracking occurred as a first float ambiguity and introducing into the state vector a second float ambiguity for the signal after resuming tracking.
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46. Rover comprising an apparatus according to claim 24.
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47. Network station comprising an apparatus according to claim 24.
Specification