On 2008-07-02, Otavio Exel wrote:
hello All,

I've been told (long time ago) that out of (and "far away from") the USA
it is *better* to turn WAAS OFF! that WAAS could actually give *less*
precision; is this correct?

I'm at -23,-46 (south america, brazil, sao paulo) and WAAS has been
working *great* here! at the top of my building my Vista HCx precision
is (almost always) 3m; if I turn WAAS ON precision drops to 2m!

According to the image at

http://upload.wikimedia.org/wikipedia/commons/4/4b/FAA_WAAS_coverage_next_generation.jpg

you're within the satellite coverage area for WAAS. Since the ground stations
reach as far south as Mexico and Puerto Rico, that should be close enough for
the correction factor to be useful in Brazil. Go much outside of the Western
Hemisphere, however, and you'll be out of WAAS satellite range, and you will
want it turned off.

--

Kristian Zoerhoff