[pct-l] Accuracy of DeLorme Topos
Jeff Moorehead
jeffmoorehead1 at cox.net
Thu Dec 7 15:18:19 CST 2006
>Has anyone checked the accuracy of the trail shown on
the DeLorme maps.
I agree with the stated low accuracy of the PCT's placement on the Delorme
Topos. However, there is one alternative that looks very good. The forest
service trace offered at Postholer is actually very accurate and can be
easily placed on the maps using the Delorme software. The trace was produced
using GIS algorithms to extract the 'trail-layer' from satellite data.
Prior to my hike last year, I embarked upon an ambitious project to produce
Harrison-style maps of large sections of the PCT. Although this eventually
became too time-consuming in the waning days of trip preparation, what I did
manage to produce using the trace and the Topo program was both accurate and
useful. I'm not sure where the Topo program gets its trace data, but it is
pretty far off in many cases.
As an alternative, I also uploaded the entire set of Garmin proprietary topo
maps of the PCT corridor into my Garmin 60CS prior to the trip. To me,
having a GPS with color maps is one of the best uses of this technology. The
PCT does not appear on many of the maps, but it does on all those
encompassed by National Parks, and curiously, it is very accurate in those
areas where the PCT was 'built' by subsuming other existing trails (good
examples are the Oregon Skyline Trail and the Cascade Crest Trail). On more
than one occasion, the Garmin GPS, along with its internal maps, helped me
navigate some tricky stretches. One was during a complete white-out
experienced at dusk in Oregon's Mt. Jefferson Park-- I relocated the trail
using the map/GPS combo. Besides, it was fun to always check position and
linear distance to landmarks such as Mt Shasta, the Canadian border, and
Campo. Gave me something to do during those boring rest stops.
Whiptail
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