Re: [Philmont]: GPS

In a message dated 03/10/2003 2:57:07 PM Central Standard Time,
SIHIWI@aol.com writes:

> Many of you seem to know about GPS so I thought I would ask for help. Last
> trek I took my Magellan 315 and although I thought I had all set correctly,
> it only recorded 35 miles. Not possible. I had waypoints set at each
> stop, and they appear to be correct. I did have it horizontal in a pouch
> on top of my bag. Any ideas? I hate to waste the lists time on this, but
> it was very annoying to not have it work right and maybe we can save
> someone else from having the same problem this year. BTW, it worked great
> around the neighborhood.
>
> Going back in 2003!!
> YIS(P)
> Bruce

Not a waste of list time at all.

GPS in the mountains is a fickle system. Although very accurate, the signals
are very weak and anything will interrupt their clear reception.

I have noticed that if you have it on when you walk into a canyon, it is much
better than turning it on in there. In either case, many sat signals are
shielded from the receiver by cliffs, rocks, trees and clouds. These all
reduce the ability of the receiver.

The Magellan 315 is designed to be held vertical to orient the antenna
correctly. Since you state you carried it horizontally, I suspect this was
the problem.

Not so much in taking a waypoint manually, but in the tracking feature. Also
remember that in the tracking mode it is saving waypoints and measuring a
straight line from point to point, not the curve of the trail. This does
shorten it considerably.

I have a "fudge factor" that I measure my mileage by when paddling on various
rivers to give a more accurate distance. The GPS always measures short, but
not 35 miles on a 65 mile trek short. You did not say what trek you went on
but none are 35 miles total mileage.

I have a 315 and have used it extensively to track my path. It works well
when held in the open in vertical orientation, but has a lot of difficulty in
other orientations.

To accommodate this, I bought a leather case for it with a spring clip and
sewed a band on my shoulder strap of my day pack just below my shoulder. I
then tether it with the strap to "catch" a fall which is inevitable.

When backpacking, I use an external frame pack and have sewed a strap on the
dies of it up high so the antenna sticks up for maximum effective reception.

GPS instruments are tools and like all tools you have to learn how to use
them if the data is going to be accurate.

I suggest to everyone I communicate with about the instruments to use them a
lot to find out these things. Playing with it in the neighborhood is a great
way to learn and exercise at the same time.

It will be interesting to see if the operators of the system, the U S
Military, tweak it when we invade Iraq. Any bets on this?

Never give up, never give up, never give up!

John LeBlanc

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Received on Wed Mar 12 16:54:45 2003