Method, carried out by 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, for estimating parameters useful to determine a position, the NSS receiver observing an NSS signal from each of a plurality of NSS satellites over multiple epochs, each of these epochs being hereinafter referred to as "receiver epoch", the method comprising: operating a filter, hereinafter referred to as "precise estimator" , that uses state variables comprising at least, but not only, ambiguities in the carrier phases, and computes values of its state variables and associated covariances, those values being hereinafter referred to as a "float solution" , based on at least one of: NSS signals observed by the NSS receiver, and information derived from said NSS signals; and information, hereinafter referred to as "reference information" , comprising at least one of: observations from at least one reference NSS receiver, and information derived from said observations; obtaining information, hereinafter referred to as "seeding information" , comprising at least one of: (i) a position of the NSS receiver and associated covariances, (ii) tropospheric delay information and associated covariances, and (iii) ionospheric delay information and associated covariances; and the method characterised in that if further comprises: computing a constrained solution, hereinafter referred to as "seeding- and ambiguity-constrained solution" , by constraining the ambiguities of the float solution from the precise estimator by the seeding information , by resolving the resulting pre-constrained ambiguities, and by constraining at least one of the other state variables of the precise estimator by the resolved ambiguities. operating a filter, hereinafter referred to as "precise estimator" , that uses state variables comprising at least, but not only, ambiguities in the carrier phases, and computes values of its state variables and associated covariances, those values being hereinafter referred to as a "float solution" , based on at least one of: NSS signals observed by the NSS receiver, and information derived from said NSS signals; and information, hereinafter referred to as "reference information" , comprising at least one of: observations from at least one reference NSS receiver, and information derived from said observations; at least one of: NSS signals observed by the NSS receiver, and information derived from said NSS signals; and information, hereinafter referred to as "reference information" , comprising at least one of: observations from at least one reference NSS receiver, and information derived from said observations; obtaining information, hereinafter referred to as "seeding information" , comprising at least one of: (i) a position of the NSS receiver and associated covariances, (ii) tropospheric delay information and associated covariances, and (iii) ionospheric delay information and associated covariances; and the method characterised in that if further comprises: computing a constrained solution, hereinafter referred to as "seeding- and ambiguity-constrained solution" , by constraining the ambiguities of the float solution from the precise estimator by the seeding information , by resolving the resulting pre-constrained ambiguities, and by constraining at least one of the other state variables of the precise estimator by the resolved ambiguities. (i) a position of the NSS receiver and associated covariances, (ii) tropospheric delay information and associated covariances, and (iii) ionospheric delay information and associated covariances; and <EOS>