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?

WAAS and other satellite-based augmentation systems like EGNOS (which is
not yet operational) are not available worldwide. IGC stands for
International Gliding Commission, which is why WAAS is not quite a good
enough solution at the moment...

Marc