A differential GPS landing system having at least three GPS receivers at known locations in spatial proximity to each other, wherein each GPS receiver independently receives GPS signals from the plurality of GPS satellites and at least three reference stations, wherein each reference station receives a signal from a different two of the at least three GPS receivers and calculates two separate differential corrections for each satellite, wherein each differential correction is independently calculated using the signals received from a different one of the two GPS receivers. The reference stations preferably average the two calculated differential corrections for each satellite to produce an averaged differential correction for each satellite. The system then validates the averaged differential correction for each satellite calculated by each reference station using two integrity monitors, wherein each integrity monitor receives the averaged differential corrections from a different two of the at least three reference stations, and each integrity monitor compares, with respect to each GPS satellite, the averaged differential corrections from the two of the at least three reference stations to produce a validated set of differential corrections, and broadcasts the averaged differential correction for each satellite calculated by one of the three reference stations. The preferred differential GPS landing system further includes a method that utilizes current differential correction error statistics, prior differential correction error statistics and a Bayesian interval estimation bounding process to provide an error bound on the broadcast differential corrections.