Stochastic modelling of the ionosphere for fast GPS ambiguity resolution

Integer carrier phase ambiguity resolution is the key to precise GPS positioning. For baselines over 10 km the errors due to the ionosphere limit the ability to resolve the integer ambiguities within short observation time spans. Of course, one can estimate the ionospheric delays, but the additional unknowns in the model limit the use of very short time spans. On the other hand, very short time spans can be successfully used by not estimating the delays at all, but only if the ionospheric delays in the data are within certain bounds.