Patent Document ID: 20140292573
Application ID: 14101119
Patent Flag: 0

Claim One:
1. Method, carried out by a computer or set of computers, for generating accuracy information for an ionosphere model calculated using a parameter estimation procedure based on phase observations made using a plurality of ground stations, wherein each phase observation is obtained from at least two signals transmitted from a satellite to a ground station, each of the at least two signals having a different frequency, and the accuracy information is usable in a GNSS positioning system for estimating a position of a rover, the method comprising the steps of: for each of at least some of the phase observations having fixed or converged ambiguities, obtaining phase residual information of the parameter estimation procedure; and computing coordinates of a pierce point on a sphere around the earth, the sphere being defined by an ionosphere single layer model, wherein the coordinates indicate where the path of the signals from which the phase observation has been obtained pierces the sphere; mapping, for each pierce point, the phase residual information of the corresponding phase observation to the vertical at the pierce point to generate vertical residual information; for each of at least some of the points of an equidistant grid on the sphere, each point being hereinafter referred to as “grid point”, identifying pierce points within a threshold distance from the grid point on the sphere; selecting grid points for which the number of identified pierce points exceeds a threshold number; computing, for each selected grid point, vertical accuracy information at the selected grid point based on the vertical residual information of the identified pierce points, and a scale factor based on the vertical accuracy information computed for the selected grid point; and generating the accuracy information for the ionosphere model based on the vertical accuracy information computed for the selected grid points, and an overall scale factor computed based on the computed scale factors.