Method for generating correction information associated with at least one global or regional navigation satellite system receiver, hereinafter abbreviated as NSS receiver, wherein the correction information comprises information for correcting pseudorange observations useful for determining a position of the at least one NSS receiver, the correction information comprising estimated receiver code biases per satellite, the method comprising: receiving raw observations obtained by one of the at least one NSS receiver observing NSS multiple frequency signals from a plurality of NSS satellites over multiple epochs, the raw observations comprising code pseudorange and carrier phase observations; obtaining information, hereinafter referred to as "precise satellite information", on: (i) the precise orbit position of each one of the plurality of NSS satellites, (ii) a precise clock offset of each one of the plurality of NSS satellites, and (iii) a set of biases associated with each one of the plurality of NSS satellites, or information derived from the precise satellite information; estimating ambiguities in the carrier phase of the received raw observations, using the precise satellite information, or using the information derived from the precise satellite information; computing combination values based on the received raw observations together with the estimated ambiguities, to cancel out the effects of the satellite motion relative to the at least one NSS receiver, the effects of the clocks, the effects of the troposphere and the effects of the ionosphere, the computed combination values defining an observation equations system; and generating the correction information per satellite, based on the computed combination values, by solving the observation equations system of the computed combination values, to estimate the receiver code biases per satellite. receiving raw observations obtained by one of the at least one NSS receiver observing NSS multiple frequency signals from a plurality of NSS satellites over multiple epochs, the raw observations comprising code pseudorange and carrier phase observations; obtaining information, hereinafter referred to as "precise satellite information", on: (i) the precise orbit position of each one of the plurality of NSS satellites, (ii) a precise clock offset of each one of the plurality of NSS satellites, and (iii) a set of biases associated with each one of the plurality of NSS satellites, or (i) the precise orbit position of each one of the plurality of NSS satellites, (ii) a precise clock offset of each one of the plurality of NSS satellites, and (iii) a set of biases associated with each one of the plurality of NSS satellites, or information derived from the precise satellite information; estimating ambiguities in the carrier phase of the received raw observations, using the precise satellite information, or using the information derived from the precise satellite information; computing combination values based on the received raw observations together with the estimated ambiguities, to cancel out the effects of the satellite motion relative to the at least one NSS receiver, the effects of the clocks, the effects of the troposphere and the effects of the ionosphere, the computed combination values defining an observation equations system; and generating the correction information per satellite, based on the computed combination values, by solving the observation equations system of the computed combination values, to estimate the receiver code biases per satellite.