David Reinhart wrote:
One of the advantages of WAAS is that it can provide approaches with
vertical guidance to minimums that are better than non-precision approaches
but worse that an ILS *without* the full ALS, etc. At my home airport that
could often make the difference between missing the NDB approach and going
to the nearest airport with an ILS or landing and driving my own car home.

Well, it depends upon the airport of course, but around here the
above frequently describes what you get w/ a non-precision GPS approach.
For example UNO (West Plains MO), the VOR 36 will get you to 672 agl;
the GPS 36 will get you to 372 agl (what a GPS approach with a clean
obstruction path can do for ya; in the other direction it's only 412).

The idea being you can get a whole lot more utility for no additional costs
for ground-based infrastructure.

What minimums would an ILS with no ALS get you? a WAAS approach?
Even if it's down to 200 AGL, is 172 ft worth $886 million? Holy
cow, and I'm a big fan of GPS approaches!

Cheers,
Sydney