[OSM-newbies] Detect WAAS/EGNOS mode

[ael]

I am a bit rusty on WAAS, but surely a major point has been missed so
far? The corrections are made with one (or a very few) ground stations
sampling the ionsphere disturbances on the path between those points and
the satellites. If your unit is "seeing" a different part of the
ionsphere, then the corrections maybe be wrong for your path. So it
depends on how uniform the ionsphere is at a particular time. And how
close you are to a ground station.

I may be wrong about this...

ael