System and method for determining gnss positioning corrections

A method for generating satellite corrections comprising:

• a) receiving satellite observations associated with a set of satellites at a reference station;
• b) modelling at least one of ionospheric or tropospheric effects as a function of least one of a pierce point or a pierce angle for satellite rays for each satellite of the set of satellites;
• c) fitting the at least one of ionospheric or tropospheric effects to a plurality of polynomial functions, wherein each polynomial function is valid within a unique geographic region, wherein adjacent unique geographic regions are overlapping;
• d) determining a set of grid points comprising residuals of the polynomial fit to the at least one of ionospheric or tropospheric effects model;
• e) determining a locality of the GNSS receiver;
• and
• f) determining the satellite corrections from:
• a polynomial function, of the plurality of polynomial functions, associated with a geographic region matching the locality of the GNSS receiver;
• and
• an interpolated residual determined from grid points proximal the locality of the GNSS receiver.