GNSS signal processing methods and apparatus with ambiguity selection

Abstract

Methods and apparatus are provided for estimating parameters, i.e. ambiguities, derived from GNSS signals. Observations of a GNSS signal from each of a plurality of GNSS satellites are obtained (2120). The observations are fed to a filter having a state vector comprising a float ambiguity for each received frequency of the GNSS signals (2140). The filter estimates a float value for each float ambiguity of the state vector and co-variance values associated with the state vector. Integer values are assigned to at least a subgroup of the estimated float values to define a plurality of integer ambiguity candidate sets (2160). A weighted average of the candidate sets is formed (2200). A formal precision value based on covariance values of the filter is determined (2205), the formal precision value being a measure for an achievable precision. An achieved precision value of the weighted average is determined (2210). The achieved precision value is compared with the formal precision value to obtain a convergence value (2215). A convergence of the determination of the state vector is indicated (2218). Ambiguities of the weighted average can be used in subsequent operations to aid in determining a position of the receiver or can be used to prepare data, e.g., in a network processor that can be used to augment position information of a rover.

Description

[0001] Related applications [0002] This application claims the benefit of US Provisional Patent Application 61 / 189,382, filed August 19, 2008, the contents of which are hereby incorporated by reference. technical field [0003] The present invention relates to position estimation methods and devices, and in particular to such methods and devices based on navigation satellite system signals. Fields of application of these methods and devices include, but are not limited to, navigation, map making, land surveying, civil engineering, disaster prevention and mitigation, and scientific research. Background technique [0004] 1 Introduction [0005] Global Navigation Satellite Systems (GNSS) include the Global Positioning System (GPS) (USA), GLONASS (Russia), Galileo (Europe) and COMPASS (China) (systems in use or in development). GNSS typically uses multiple satellites orbiting the Earth. The plurality of satellites form a constellation of satellites. GNSS receivers detect ...

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[0053] However, the practical disadvantage of the floating-point solution is that although it converges, doing so is time-consuming

As in [1], page 34, lines 3-6 "Due to the high correlation between the individual ambiguities, the search space in the case of GNSS is extremely elongated, so that the search for the integer solution may take very long.Therefore , the search space is first transformed to a more spherical shape by means of a decorrelation of the original float ambiguities (due to the high correlation between the various ambiguities, the search space in the case of GNSS is extremely stretched, thus making the The search for an integer solution can be time consuming

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