Patent ID: 11885890
Assignee: U-BLOX AG
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 8:
9. A computer-implemented method for global navigation satellite system (GNSS) measurements, the method comprising:
specifying, in advance, a prior probability density P(x) of a state x;
specifying, in advance, a system model h(x) that relates the state x to observables z of the measurements;
quantifying, during the measurements, quality metrics q associated with the measurements;
specifying, in advance, a non-Gaussian residual error probability density model ƒ(r|θ, q) and fitting model parameters θ determined off-line a priori, where r is a residual error;
defining, during the measurements, a posterior probability density P(x|z, q, θ);
estimating, during the measurements, the state x; and
computing, during the measurements, a protection level of a position estimate by integrating the posterior probability density P(x|z, q, θ) over the state x,
wherein integrating the posterior probability density over the state x comprises:
performing a first round of sampling by drawing a first set of samples from an unbiased distribution of the posterior probability density and estimating a first location of a quantile on the first set of samples;
performing a second round of sampling by drawing a second set of samples from a first constrained distribution of the posterior probability density that is determined based on the first location of the quantile;
estimating a second location of the quantile on the second set of samples, wherein the second location of the quantile is used to set a second constrained distribution for a third round of sampling;
repeating the sampling using a constrained distribution set in previous sampling until nth round of sampling is completed, where n is a natural number greater than 2;
determining whether samples of the n round samplings are adequate for computing the protection level; and
combining the samples of n rounds sampling with appropriate weights when the samples of n rounds are adequate for computing the protection level.