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 at least one NSS signal from each of a plurality of NSS satellites over multiple epochs, the method comprising: operating an estimation process, hereinafter referred to as "estimator", for an epoch, hereinafter referred to as "previous epoch", wherein the estimator uses state variables and computes the values of its state variables at least based on time-differenced observables, hereinafter referred to as "delta observables", computed for the previous epoch, wherein the delta observables for the previous epoch are computed by differencing NSS observables observed by the NSS receiver at the previous epoch and NSS observables observed by the NSS receiver at an epoch preceding the previous epoch, and wherein the observed NSS observables comprise at least one of: carrier phase observables, and code observables; obtaining residuals, hereinafter referred to as "previous residuals", from the estimator, each previous residual being associated with a delta observable computed for the previous epoch; for each of at least some of the delta observables, adjusting the previous residual associated with the delta observable, wherein adjusting comprises multiplying the previous residual with a coefficient, hereinafter referred to as "back-residual coefficient"; computing delta observables for another epoch, hereinafter referred to as "current epoch", the current epoch following the previous epoch, wherein computing the delta observables for the current epoch comprises differencing NSS observables observed by the NSS receiver at the current epoch and NSS observables observed by the NSS receiver at the previous epoch, and wherein the observed NSS observables comprise at least one of: carrier phase observables, and code observables; for each of at least some of the delta observables, correcting, using the adjusted previous residual associated with the delta observable, the delta observable computed for the current epoch; and operating the estimator for the current epoch at least based on the corrected delta observables. operating an estimation process, hereinafter referred to as "estimator", for an epoch, hereinafter referred to as "previous epoch", wherein the estimator uses state variables and computes the values of its state variables at least based on time-differenced observables, hereinafter referred to as "delta observables", computed for the previous epoch, wherein the delta observables for the previous epoch are computed by differencing NSS observables observed by the NSS receiver at the previous epoch and NSS observables observed by the NSS receiver at an epoch preceding the previous epoch, and wherein the observed NSS observables comprise at least one of: carrier phase observables, and code observables; carrier phase observables, and code observables; obtaining residuals, hereinafter referred to as "previous residuals", from the estimator, each previous residual being associated with a delta observable computed for the previous epoch; for each of at least some of the delta observables, adjusting the previous residual associated with the delta observable, wherein adjusting comprises multiplying the previous residual with a coefficient, hereinafter referred to as "back-residual coefficient"; computing delta observables for another epoch, hereinafter referred to as "current epoch", the current epoch following the previous epoch, wherein computing the delta observables for the current epoch comprises differencing NSS observables observed by the NSS receiver at the current epoch and NSS observables observed by the NSS receiver at the previous epoch, and wherein the observed NSS observables comprise at least one of: carrier phase observables, and code observables; carrier phase observables, and code observables; for each of at least some of the delta observables, correcting, using the adjusted previous residual associated with the delta observable, the delta observable computed for the current epoch; and operating the estimator for the current epoch at least based on the corrected delta observables.