Re: [Paddlewise] GPS - FYI

From: Michael Neverdosky <MichaelN_at_cycat.com>
Date: Fri, 26 Mar 1999 05:56:55 +0000
The problem of the track function is caused by the basic error in the GPS
system
and by selective availability (SA).
The problem is timing accuracy of the signals from the satelites and can't
be 
fixed byanything in the receiver without receiving additional signals,
i.e.
using differential GPS (DGPS). Survey quality instruments get better
accuracy
by staying in one place during the fix and also by saving the data for
additional
processing later.

This is a classic navigation problem, a time error translates into a
position error
of a certain distance.

The faster you are going the smaller the error is compared to the actual
movement.
At walking and kayak speeds (also most sailing speeds) the basic errors of
the
system are large compared to the distance you are traveling in each update
period (typically 1 second), so your speed and direction of travel
displays
are not very usefull.

As for the display of waypoints, you are generally stuck with whatever the
programmers
thought was a good idea. If you can carry a computer then you can use a
mapping/GPS
display program to display things in any form you want. Unfortunately,
this is not
very usefull on a kayak underway.

michael

bhansen97_at_aol.com wrote:
> 
> Woody - Garmin was amazingly available by phone today. The tech rep said the
> tracking function does not work at speeds lower than about 3.3 knots.
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Received on Fri Mar 26 1999 - 02:57:24 PST

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