[pct-l] RE: Topo!Trails trace of the PCT [California]

Re: Topo! map of PCT in California

Roger-
a. Distance. In general distance and elevation readings taken from trail
tracings on Topo! depend entirely on how carefully and accurately one traces
the trail. If you don't have an actual line on the map that represents the
trail it is virtually impossible to reproduce the way a trail winds in and
out of gullies etc, etc, etc. For about 50% of the distance the trail was
displayed on the actual map. Under these conditions the distance and
altitude readings are very accurate. I traced the trail on level 5, the most
detailed level on Topo!

On the other hand, where there is NO trail on the map, I followed the
guidebook route. This was a case of locating the elevation contour line that
the trail was following according to the guidebook, then drawing in the
trail over that specific contour line on the electronic map. In this case I
suspect that the switchbacks are not all that accurate so the distance will
be less than actual and the rate of elevation gain/loss higher.

b. Accuracy versus a GPS route

I believe it was Doug Gates who attempted to walk, and GPS plot the trail.
He had the usual thruhiker problems compounded, no doubt, by the additional
weight required to trace the trail via GPS, and dropped out. However,
comparison of the trace he produced and the trace that I created from the
guidebook showed very little varience. Accordingly, I believe the
topo!trails trace I have is reasonably accurate -- except where I have made
a mistake.

I have reported to Bob at PCTA and Tom at Topo! that I believe that my trace
is as good as we are going to get without specifically tracing the trail
with a GPS in a proper fashion, as opposed to having a thruhiker trace the
trail as an afterthought. I plan to do this in 2002 for California. I don't
think a continuous waypoint setting is good enough. I will manually pick up
a waypoint at every inflection point on the trail, thus accurately recording
the meanderings and switchbacks the trail takes. The new 12 satelitte
systems seem to work very well even with forest cover. Sometimes however you
simply have to stop at an open area to allow the GPS to get its bearings and
take a waypoint reading at that point.

Until then my goal is to go over the trace I have made and correct any
errors. In some cases the guidebook and the map disagree as to the route. In
this case I have either shown both routes or prefered the guidebook.

Regards,
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