[time-nuts] Weird T-Bolt elevation readings...

[Didier Juges]

To tell you how far above ground you are, the GPS has to know where the ground is. For that, it is using a model that is not perfect. That is why John Miles' GPS tells him he should get his scuba gear immediately...

If you google "geoid" you will find more than you wanted to know about it.

Didier

------Original Message------
From: Michael Baker
Sender: time-nuts-bounces at febo.com
To: Time-Nuts
ReplyTo: Time-Nuts
Subject: [time-nuts] Weird T-Bolt elevation readings...
Sent: Jan 14, 2010 2:28 PM

Hello, TimeNutters--

While we are on a thread about Trimble T-bolts,
perhaps someone might expand on why my T-bolt
does not ever come up with altitude readings that
are even close.  After a long fix, the Lat-Lon
coordinates are pretty close, but the altitude
is always given as around 2 meters.  We are pretty
low here in Flori-DUH, but not THAT low.  My
ground elevation here is 28M ABMSL and my
GPS antenna is another 8M above that on top
of my fireplace chimney.  I have roughly 50 ft
of RG-59 cable on the antenna, but altering the
cable length value does not seem to have any
effect.  I get these same very low altitude readings
with TBOLTMON and Lady Heather v3 beta.

Since I know my altitude well withing one meter,
should I enter that manually?  What is the
procedure for doing that?

Suggestions...??

Thanks!!

Mike Baker
-------------------



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------------------------ Sent from my BlackBerry Wireless thingy while I do other things...