RE: [pct-l] The PCT GPS Mapping Project

Tom wrote:
>
You must collect waypoints either every 200 yards or every inflection point
[a point where the trail changes direction, at a switchback for example].
The GPS only holds 500 way point so you must record the waypoints [on paper]
and clear the GPS about every 30 miles [about once per day]. This requires
recording the latitude and longitude of 500 points. This could easily take a
couple of hours.
>

I think this is a great idea and I look forward to seeing the results.
However, I want to point out that this project is probably not suited for
people attempting a thruhike.  Accurate mapping with a consumer-grade,
handheld GPS requires a lot of work to collect accurate data.  I' not
intending to torpedo Tom's project, but I think it would be better in the
long run if the volunteers understand what they're getting into so the
resulting data are of useful quality.

I've done some GPS trail mapping here in Washington and it works reasonably
well if you take the time to do it right, but it's a pain in the butt when
you're trying to get someplace on a schedule.  At every waypoint, you have
to stop, remove the GPS from its stowed position, hold it upright and away
from your body to get good reception, check the estimated precision error,
move around a bit if necessary to get an accurate fix, record the waypoint,
restow the GPS, and continue walking.  And you've got to do this every 200
yards, or at every change in trail direction.  And if you forget and blow
past a switchback without recording it, you've got to retrace your steps to
pick it up.

As Tom pointed out, consumer-grade GPS units have rather limited memory,
which means you can only map a relatively short distance before having to
dump the recorded waypoints to some other medium (either computer or paper)
in order to continue.  Spending the evening writing down 500 Lat/Long pairs
_after_ walking 20 miles is not something most people have the discipline to
do day after day.  And then there's the inevitable transcription errors.

Also, battery life in a GPS is relatively short - most run 15 hours or less.
At the distance resolution Tom's talking about (200 yards), I don't think it
would be worth it to turn on the GPS for every waypoint and turn it back off
again, so standard batteries are only going to last a single day.  Lithium
batteries can extend that life significantly, of course, but you'll still
need to plan on carrying several spare sets of batteries.  That might cause
ultra-lights to have heart failure at the mere thought.  :-)

It's possible to invest in equipment that makes the job much easier.  An
external antenna unit, mounted on a pole attached to your backpack so that
it's above your head, would allow you to record a continuous track without
having to worry about reception problems - no stopping and starting.  A
sub-notebook computer (or a more expensive GPS) would allow you to record
all the waypoints you wish without severe storage limits.  A big lantern
battery or two would provide power for the whole setup.  But you're talking
about a serious chunk of money and weight there.  Plus you'd look
ridiculous.  :-)

I encourage everyone to help out with this who's able to.  Having an
accurate GPS track of the PCT is useful in many ways; trip planning,
resource protection, trail construction and maintenance, etc.  Just make
sure that you'll be able to devote the energy necessary to do a good job.

By the way, Tom, are you interested in mapping the Washington portion of the
PCT?  I've got some already, and can do more.

Eric
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To:            "Reynolds, WT" <reynolds@ilan.com>, <Bighummel@aol.com>, <pct-l@backcountry.net>