[pct-l] Follow-up to the earlier GPS discussion

[CHUCK CHELIN]

Good Gary, ,

The PCT is a great trail for a minimalist to navigate:  It’s wide, well
maintained, well marked, and for 99% of its length very easy to find and
walk.  When encountering an area of confusion, such as extensive snowpack,
fog, etc. one has only to wait a while and someone will hike by with good
information:  Just follow them.



Navigating alone with just a map and a compass is a challenge, and the very
well-marked nature of the PCT occasionally exacerbates the problem.  To be
effective with only a map and compass it is necessary to maintain close and
ongoing situational awareness of the terrain by looking at the map regularly
and always rationalizing the apparent terrain with the terrain depicted on
the topo’ map.  When doing so, one must stop instantly whenever there is a
real-vs-map disconnect or inconsistency and do whatever is necessary to
resolve the issue before proceeding further.  Any continued travel without
resolution is most likely to increase the confusion rather than resolve it.



That’s the problem on the PCT:  Walking and trail-finding is super easy for
miles – hundreds of miles – at a time.  As a result, it’s easy to become
situationally disconnected from one’s progress on the map by admiring the
views rather than thinking about what’s actually unfolding.  The result is
one can be led down the wrong trail.  Over snowpack it’s really easy to miss
a course change at a switchback, miss a trail junction, or just wander to
the left or right.  Other tracks may help or hinder, but soon nothing looks
right and we find ourselves on the wrong ridge or in the wrong drainage
entirely – in a word, lost.



So …. what to do?  We whip out the trusty compass – accurate to 1-2 degs. –
and find north.  Unfortunately, that won’t pass the all-important, “So
what?” test:  We don’t know where we are, we don’t know there the trail is,
and we don’t know if we are to the left or the right of the trail.  We don’t
even know if the trail is 10 feet away or 2 miles.  All we know for sure is
that with the compass we can travel in whatever direction we choose without
going in typical lost-hiker circles.



The best bet then is to backtrack to try to find some point that we are
confident we can identify on the map, which is easier said than done.  If we
got lost by not paying attention, how will be get un-lost by now trying to
go backwards through terrain we didn’t pay attention to in the first place?
Snow is great in those circumstances:  Maybe we can follow our own tracks
backswords – maybe.



This is where a good altimeter, and a good understanding of its use and
limitations, can add another valuable piece of information: If we don’t know
the “X” of our location, or the “Y”, maybe a good “Z” level, i.e. an
elevation, can help when looking at the topo’ map.  For that very reason I
carried an altimeter for years before I got a GPS, however I found that my
favorite altimeter – a PEET Model 88 – weighs 3.6 ounces while my GPS weighs
3.5 ounces.  I can usually read the PEET to within 10 feet of elevation –
assuming I’ve regularly maintained its calibration – while the GPS elevation
may only be accurate to 100-200 feet, but so what?  With precise “X” and “Y”
coordinates I no longer need the “Z” at all.



I love compasses.  I have many -- from a piece of magnetite hanging on a
fine string to a beautiful 9.8 ounce *Leupold & Stevens Cruiser* model – but
I will not represent that they can produce an accurate location,
particularly under probable field conditions.  Compass results are far less
accurate than those of a GPS -- yes, several orders of magnitude less
accurate.  The best compass-derived coordinates are had when triangulating
from at least two known terrain features.  We’ll assume for a moment that we
can actually see those features in the fog, overcast, rain, or dusk/dawn
light, and from within heavy timber.  If those features are five miles away
– which is close in practice – and if one can identify the exact point and
read the bearing to plus/minus one degree of accuracy, the potential error
is over 900 feet.  That’s better than nothing, but it’s far worse than the
normal GPS system accuracy not to mention the more precise WAAS accuracy.



Steel-Eye

Hiking the Pct since before it was the PCT – 1965

http://www.trailjournals.com/steel-eye

http://www.trailjournals.com/SteelEye09


On Thu, May 20, 2010 at 2:57 PM, Gary Schenk <gwschenk at socal.rr.com> wrote:

> On 5/20/2010 8:37 AM, CHUCK CHELIN wrote:
> >
> > In terms of accuracy, GPS locations are several orders of magnitude
> better
> > than compass-based locations.  When I hear someone criticize GPS accuracy
> > I’m led to believe that they’ve never tried to locate their position on a
> > topo’ map by triangulating from the peaks of surrounding mountains --
> > assuming they can actually see peaks; assuming they know for sure which
> > peaks they’re looking at; and assuming they can identify which of the
> many
> > bumps on the ridge is actually the peak.  It’s particularly difficult in
> the
> > Sierras where there are many peaks all strung together on ridges, but
> it’s a
> > bit easier in the Pacific NW where the tall volcanoes usually stand
> > prominent and alone.  There the problem is the peaks are mostly in a
> > north-south line and it’s hard to get something at 90 degs. to form a
> > triangle.
>
> As a minimalist, rather than ultra-light, hiker I don't carry a GPS.
> It's basically unnecessary weight. Not only are you carrying the GPS,
> but also extra batteries and/or a gizmo to charge those batteries. A
> compass and map is more than sufficient for navigating a hiker. A
> commercial handheld GPS is not orders of magnitude more accurate than
> map and compass, depending on operator error, of course. An altimeter is
> much more useful and practical as a navigation aid, IMHO.
>
> Most of my navigation is done only with a map. The ability to read a map
> and the terrain around you is a valuable skill that all hikers should
> develop.
>
> YMMV HYOH, etc.
>
> Gary
>
>
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