writes:

You don't understand how WAAS works.

The corrections are to grid points based on observables from multiple
reference stations.

The corrections are based on data from only 29 stations, but they are
extrapolated to an entire continent. This inevitably increases
inaccuracies. It's as simple as that.

That's why LAAS exists, which uses reference points that are at the
same location as the location for which corrections are being
provided.

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