Patent ID: 9513374
Filing Date: 2016-12-06
CPC Classification: G01S

Claim Text:
1. A method of operating a navigation assistant that includes a Global Navigation Satellite System receiver, comprising: determining in circuitry in a the Global Navigation Satellite System receiver a first pseudorange from a first Global Navigation Satellite System satellite; determining in the Global Navigation Satellite System receiver circuitry a reference range from a reference position to the first GNSS satellite; determining in the Global Navigation Satellite System receiver circuitry a measurement error as a function of the difference between the reference range and the first pseudorange; weighing in the Global Navigation Satellite System receiver circuitry the first pseudorange by the measurement error; computing a position solution from a set of pseudoranges that include the weighed first pseudorange, the position solution includes at least one of a position, velocity, and error covariance and the reference position is an a priori position estimate of a Kalman filter determined from a prior position; determining in the Global Navigation Satellite System receiver circuitry a measurement error covariance as function of the difference only if the measured pseudorange is greater than the reference pseudorange; computing the measurement error covariance in the Global Navigation Satellite System receiver circuitry at least partially according to: in which R represents the error covariance, Δρrepresents a residual pseudorange error of the first set of satellites, H represents an n×4 matrix comprising unit vectors pointing from an approximate user position to the n visible satellites, C represents an estimate of error covariance from term E[(ΔX)(ΔX) T ], N is an integer representing an observation window, the operator T represents a transpose operation and the operator, Σ represents a summation operation; determining in the Global Navigation Satellite System receiver circuitry a second measurement error as function of a correlation peak shape; modifying, in the Global Navigation Satellite System receiver circuitry, the measurement error based on the second measurement error; and providing the measurement error based on the second measurement error to the navigation assistant.