On Feb 25, 8:00*pm, vontresc wrote:
Just to throw some more fuel on the fire here. What about WAAS enabled
GPS. If the derived altitude is good enough for a quasi ILS approach
to 250' , shouldn't this be good enough for a flight logger?

I don't think WAAS enabled GPS is available throughout the gliding
world. Whatever solutions are acceptable to the IGC have to be
available anywhere that people are flying, not just in the US:

http://www8.garmin.com/aboutGPS/waas.html

Who benefits from WAAS?

Currently, WAAS satellite coverage is only available in North America.
There are no ground reference stations in South America, so even
though GPS users there can receive WAAS, the signal has not been
corrected and thus would not improve the accuracy of their unit. For
some users in the U.S., the position of the satellites over the
equator makes it difficult to receive the signals when trees or
mountains obstruct the view of the horizon. WAAS signal reception is
ideal for open land and marine applications. WAAS provides extended
coverage both inland and offshore compared to the land-based DGPS
(differential GPS) system. Another benefit of WAAS is that it does not
require additional receiving equipment, while DGPS does.

Other governments are developing similar satellite-based differential
systems. In Asia, it's the Japanese Multi-Functional Satellite
Augmentation System (MSAS), while Europe has the Euro Geostationary
Navigation Overlay Service (EGNOS). Eventually, GPS users around the
world will have access to precise position data using these and other
compatible systems.