Methods and systems for positioning purposes

System comprising at least one of a navigation satellite system receiver, hereinafter abbreviated as “NSS receiver”, and a processing entity capable of receiving data from the NSS receiver, the system being for estimating parameters useful to determine a position, the NSS receiver observing NSS signals from each of a plurality of NSS satellites, and the system being configured for:

• obtaining information, hereinafter referred to as “multipath-related information”, indicative of an expected or estimated level of multipath where an antenna or antennas of the NSS receiver is or are located;
• determining a positively skewed distribution based on the multipath-related information;
• and
• operating an estimation process, hereinafter referred to as “estimator”, wherein the estimator uses state variables, computes values of its state variables at least based on NSS code observations by the NSS receiver, and operates under an assumption that errors in the NSS code observations follow the determined positively skewed distribution.