[BULK] - RE: [pct-l] GPS Altimeters

[msaenz at mve-architects.com (Mike Saenz)]

You need three to triangulate (the "tri" in triangulate....).
Four for altitude.

The more satellites locked onto, the greater the accuracy.

WAAS enabled units include the ability to receive signal from LAND based
signal stations.
Since land based stations are relatively unaffected by atmospheric
disturbances, they provide a more reliable/accurate additional reference
for GPS's to locate themselves on. 


Michael Saenz, Associate Partner
McLarand    Vasquez    Emsiek   &   Partners,   Inc.
A r c h i t e c t u r e  |  P l a n n i n g  |  I n t e r i o r s
MVE       MVE    Institutional       MVP    International
w  w  w   .   m  v  e   -   a  r  c  h  i  t  e  c  t  s   .   c  o m

-----Original Message-----
From: pct-l-bounces@mailman.backcountry.net
[mailto:pct-l-bounces@mailman.backcountry.net] On Behalf Of Eric Lee
(GAMES)
Sent: Monday, September 19, 2005 9:42 AM
To: vichanson@juno.com; pct-l@mailman.backcountry.net
Subject: [BULK] - RE: [pct-l] GPS Altimeters

Vic wrote:
>
I am still confused on GPS units, please help! The more expensive ones
have a barometric altimeter. Acording to the Garmin website, it takes
two sats to get a location, three to get altitude. I take this to mean
that any GPS can give you the altitude reading, it this correct? If so,
what is the advantage of having a barometric altimeter in a GPS? I was
with a friend a few weeks ago, he was using a Garmin Summit. When he
checked the altitude, it asked if he wanted to calibrate by satelite.
When he did, it showed an altitude over 500 feet greater (we were at
16,000', in a car, having lunch!).
>

Well, I would hope that the people at Garmin knows what they're talking
about, but all the information I've ever read says that three satellites
are required to get the location and four are required for altitude.

Eric
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