Gnss measurement processing to identify modes

A GNSS receiver comprising:

• a signal processing unit, configured to produce a plurality of GNSS measurements, wherein the plurality of GNSS measurements includes a plurality of carrier phase measurements;
• and
• at least one processor, configured to:
• obtain the plurality of GNSS measurements;
• define a state vector, the state vector comprising state variables;
• obtain a posterior probability density for the state vector, wherein the posterior probability density is based on one or more residual error models describing a probability distribution of errors in each of the GNSS measurements, the one or more residual error models including at least one non-Gaussian model;
• perform a search to identify a set of modes of the posterior probability density;
• and
• infer state information based on the posterior probability density, using the identified set of modes,
• wherein the search comprises:
• transforming the posterior probability density into a mixture model comprising a plurality of mixture components, wherein each mixture component is a multivariate distribution;
• and
• identifying the set of modes using the mixture model,
• wherein each mode is associated with a respective one of the multivariate distributions.