Re: RC: Re: GPS units: need info.

["Duncan Fletcher" <dfletche@gte.net>]

I haven't tried to use ones with built in maps. I question their
topographical resolution/accuracy. Let me reemphasize one of David's points.
Always carry an alternative - generally this means compass and map. They
will not only give you an alternative if the GPS fails (or tree cover,
mountain terrain prevents sufficient satellite coverage), the map will
answer that question about I know I am here and I want to be there, but how
do I get there from here without falling off a cliff. The Garmin GPS 12XL
has an optional remote antennae port. I have had reasonable success with the
GPS 12 (without remote antennae) in pommel bag. In my pocket is awful. In
the cantle bag would probably be better, but it isn't convenient there. An
external antennae would certainly help. I have made reference to Garmin GPS
12 and GPS 12XL. There are other brands and other models. I haven't looked
at the market in a year, and this stuff changes as fast as other computer
technology.

For download into your computer, it is not necessary to have the expensive
ones. The Garmin 12 does quite nicely. There are a couple of programs that
are capable of handling USGS digitized raster topo maps and allow tracks and
waypoints to be downloaded from the GPS onto the map or for waypoints and
tracks to be created on the map and uploaded to the GPS. I will recomend
OziExplorer. It is a shareware program that can be downloaded at
http://www.powerup.com.au/~lornew/oziexp.html. You will have to pay the
registration fee of perhaps $65 to have the ability to work with the USGS
maps. These have gotten a bit pricey from the US Government. But they are
public domain, so there are some alternative sources for the CDs. Many can
be downloaded from the web for free. But they are large files - anywhere
from 3 to 11 MB for a single 7.5 minute topo. Zipped they are smaller. You
either need a very large HD or removable medium or writeable CD. I have
downloaded most for my area and have burned them to CD.

As a speedometer in car it isn't bad. For use on foot or even horseback, it
is unreliable. The military fudge factor (usually referred to selective
availability of SA) can add or subtract 2 mph from the your true speed.
Ditto for elapsed mileage figures. The elapsed mileage will be overstated
because of off track errors caused by SA - most noticable again at slow
speeds.

For more information on GPS go to http://joe.mehaffey.com/. A lot
information, independent product reviews and links other information.

Duncan Fletcher
dfletche@gte.net


----- Original Message -----
From: David LeBlanc <dleblanc@mindspring.com>
To: Duncan Fletcher <dfletche@gte.net>; <ridecamp@endurance.net>; Jerry Kopp
<jkopp@ohio.net>
Sent: Monday, November 29, 1999 1:29 PM
Subject: Re: RC: Re: GPS units: need info.


> I also use one - with mixed results.  I also have a Garmin 12XL, and once
> used it to find my way out of several wrong turns, but another time ran
> into problems because it doesn't have any way to know what the terrain
> looks like.  Does you no good to know that camp is 3.2 miles away if you
> are on the wrong side of the mountain.  Also, one should carry non-powered
> navigation devices, as the Garmin does you no good whatsoever if the
> batteries are dead.  Spare batteries are also a good idea.
>
> There's another wrinkle to this, and I haven't done it quite yet - the
more
> expensive versions ($300 or so) can have topo maps downloaded into them.
> So if you've bought the map software that has the information, you can
have
> topographic info loaded into your unit for where you want to go - solves
> the problem with being on the wrong side of the ridge.  You can also come
> home and download where you went into the computer and use the software to
> plot maps of exactly where you went, along with how far and even what your
> total altitude changes were.  Be really nice for mapping out training
> rides, or even making sure that the ride you're putting on is really as
> long as you think.
>
> Another problem is that it doesn't pick up very well in its case, and
> although there are mounts for bicycles and cars, I haven't figured out how
> to attach it to a saddle.  The more expensive units also can use a remote
> antenna (very useful for using it in a car, too), and I think you could
pin
> the antenna to your shoulder or top of your cantle bag, and that way
you'll
> get a good recording without having to worry about it falling off the
horse.
>
> Unless cost is really critical, I'd go for the more expensive unit.  The
> cheaper ones can be useful and fun, so it depends on your usage.
>
> Oh - to answer some specific questions below - yes, you can use it as a
> speedometer.  If you don't believe me, take one in the car with you and
> check it.  Mine is very accurate IF it has a lock on several satellites.
> Same thing is true of everything else it measures - IF it has a good
> reading the whole way, then it will accurately tell you how far you went.
> Using the mapping software along with the unit with the remote antenna
> would give better results, even if there are dead spots due to heavy
foliage.
>




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