CA Sec D - Endangered Old Alternate
The information presented here was produced by the Halfmile Project, a volunteer mapping and geodata
effort coordinated by Lon Cooper ("Halfmile") and David Lippke ("White Jeep").
HISTORY: These tracks and waypoints are derived from GPS data collected every year
from 2007 through 2017 by Halfmile and over dozen other Pacific Crest Trail hikers with further input
from dozens more. In 2013, four sections (CA L-O) and portions of others were recorded with survey
grade GPS equipment by Tina and David Lippke. Those sections now have mean accuracies better
than 0.7 meter. Also in 2013, five hikers carried GPS loggers which had been custom designed
and built by Dal Brandon. In 2014, Dal, David, and Jeff Hayward worked together to design and
deploy even higher capability loggers based on the uBlox NEO-7P diffential GPS receiver.
Those were carried and operated by SOBO thru hikers John and Christine Haffner (aka Dirt Stew and
Dormouse) and also by Lon on his NOBO thru hike. In addition to the track data, these hikers collected
over 5000 geo-tagged voice notes.
ACCURACY METRICS: The efforts of 2013 and 2014 have resulted in the replacement of 90% of
all prior data for the mainline PCT (76% overall). The mean (1-sigma) horizontal accuracy is
now 1.9 meters but per section accuracy varies between 0.5 meters and 3.8 meters.
State averages for horizontal accuracy are 1.2, 2.7, and 2.8 meters for California, Oregon,
and Washington, respectively. The track data in this KML has been decimated using the
Ramer-Douglas-Peucker algorithm with an epsilon of 0.5 meters.
This KML, the Halfmile maps, and trail notes apps are updated each year. The filtering,
analysis, and final track determination is performed by David. The final waypoint set
determination and the particulars of each point are set by Lon. On the basis of geo-tagged voice
notes made by both Lon and the Haffner's in 2014, nearly 1000 new waypoints have been added and
most legacy points have had both their positions and descriptions tweaked. Several hundred waypoints
have been renamed and all trail mileages north of Tuolumne Meadows have been recomputed -- sections
north of there no longer start and end on even half mile boundaries.
2018 Track and Mileage Updates: The Sierra Buttes Realignment has replaced the mainline PCT between mile mark 1203.402 (39.601596, -120.662091)
and what was mile 1207.891281 (39.650247, -120.668375). The realigned trail adds approximately 2.35 miles to the overall
length. However, this length is expected to increase over the next year or two as the realignment is refined and the new track
is recorded with better GPS equipment. Consequently, we have decided slightly stretch the alignment's miles and add
exactly 2.5 miles to the overall trail mileage. Also note that the realigned section was recorded with basic GPS equipment
that did not provide per-point accuracy information. The accuracy metrics stated above do not hold for this new section.
In addition to the track and mileage changes, a great many waypoints have been renamed for 2018.
WARNING: As a result of the major changes described above, the 2018 maps, data, and apps cannot be used with
any material from prior years. Make sure everything you have is based on 2018 data .. e.g., don't
try to use saved maps from prior years with this year's electronic data and apps.
See <a href="http://www.pctmap.net">www.pctmap.net</a> for free printable
PCT maps and <a href="http://www.halfmileproject.org">HalfmileProject.org</a> for more information.
This data is provided as a free service to PCT hikers. We do our best to ensure its accuracy,
but it may contain errors. We assemble and distribute this information in the hope that it will be
useful, but do so WITHOUT WARRANTY. Please use common sense at all times and hike safely!
----- Copyright 2018 by Lon Cooper and David Lippke -----