[Cdt-l] accurate GPX track based on the new mapbook data?

bcss at bresnan.net bcss at bresnan.net
Sat Mar 26 17:38:20 CDT 2011

In answer to Dan's question, we have not finished Montana so we don't have
yet.  We still have 400 miles up there and 500 in Wyoming then we will be
done. The goal is to finish it this summer so the earliest that MT data
could be available is 2012.  

Brett - It's not surprising to me that the gpx files you have don't match up
to the maps very well.  The gpx format is something that only exists in the
recreational  gps world so those tracks were in all probability collected
with a Garmin or Magellan using the internal antenna while attached to a
pack or waistband. That method may be fine for navigating a trail but is
seriously flawed should you desire to collect usable data. The antenna of a
gps has to be elevated above head high or the data stream is compromised by
reflections and obstructions. A gps signal bouncing off of your head can
introduce hundreds of feet of error.   

Our project data is collected using professional grade sub-meter rated gps
gear with external antennas elevated above head height. These units address
the data quality issues above but they do not support the gpx format.
Converting it to gpx requires a lengthy process to dilute the database since
the most robust track files are limited to 10,000 points. We collect more
positions than that every hour we are on the trail, so a great deal of
editing is necessary. I don't anticipate tracks being available from us
until after the initial project is complete.  The waypoints, however, are on
a 1/2 mile average spacing and the mileages between them are accurate. Get
the waypoints and maps and you will get there.    

We will begin in The Great Basin headed north in June.  Hope to see some of
you out there.  

best wishes,

Jerry Brown
GPS Mapping Specialist
The Continental Divide Trail Alliance
bearcreek at wic.net

-----Original Message-----
From: cdt-l-bounces at backcountry.net [mailto:cdt-l-bounces at backcountry.net]
On Behalf Of Brett
Sent: Saturday, March 26, 2011 12:59 PM
To: cdt-l at backcountry.net
Subject: [Cdt-l] accurate GPX track based on the new mapbook data?

> Is CDT GPS data available for MT?  Specifically, Butte area to YNP?
> Dan

Dan, this may be a question for Jerry Brown as well:

I'm trying to get ahold of an accurate GPX track for the CDT across the 
Gila National Forest. The Trailsource data ( 
http://www.trailsource.com/continental-divide-trail/index.asp ) is more 
of an approximation and the number of points in the track too few to 
provide an accurate mileage figure and elevation profile. The waypoint 
files that CDTA is generously providing ( 
www.cdtrail.org/page.php?pname=waypoints ) are as we know based on 
actual field measurements, and when overlaid on the GPX track line the 
inaccuracies of the latter become obvious. Unfortunately the waypoint 
file is too spartan to allow one to "connect the dots" in an accurate 
way, so there appears to be no way to "grow your own" track file using 
mapping software.

An accurate track file would be extremely helpful for anyone planning to 
incorporate portions of the CDT into extended routes of their own 
making, which is the punishment I've lately begun meting out for myself. 
CDT section hikers and loop hikers could also make handy use of an 
accurate source file, rather than tracing information by hand from the 
CDT mapbooks. I imagine this would resonate with a lot of folks, who 
would be more than happy to pay for this information, given the time and 
effort that went into gathering it for use in the mapbooks.

- Brett

> Message: 2
> Date: Sat, 26 Mar 2011 10:06:09 -0400 (EDT)
> From: Danandgailsc<danandgailsc at aol.com>
> Subject: Re: [Cdt-l] Cdt-l Digest, Vol 41, Issue 13
> To:cdt-l at backcountry.net
> Message-ID:<8CDB9D616C51296-18C8-1A44C at webmail-m066.sysops.aol.com>
> Content-Type: text/plain; charset="us-ascii"
> Is CDT GPS data available for MT?  Specifically, Butte area to YNP?
> Dan
>     1. Re: GPS + Map Question (Peanut Eater)
>     2. GPS&  Map Options (Rick Ostheimer)
>     3.  GPS&  Map Options (Jerry Brown)
>     4. CDTS Columbus route KML&  GPX (Brett)
> Planning on hiking Colorado  portion of CDT summer 2011.
> I understand that there are various routes, various maps, various GPS
> that are compatible with certain software.  Do I select a GPS according to
> the maps/software that I use?  Do I use Ley software? National Geographic
> Trail Illustrated software? CDTS CD Maps?  A combination of all of the
> above?
> So many choices - so many decisions.
> wyldeflower
> ------------------------------
> Message: 3
> Date: Sat, 12 Feb 2011 18:29:43 -0700
> From: "Jerry Brown"<bearcreek at wic.net>
> Subject: [Cdt-l]  GPS&  Map Options
> To:<Cdt-l at backcountry.net>
> Message-ID:<000001cbcb1d$7ff45440$7fdcfcc0$@net>
> Content-Type: text/plain; charset="us-ascii"
> Detailed gps waypoint data in gpx format for both NM and CO may be
> downloaded from cdtrail.org at no cost via this link:
> www.cdtrail.org/page.php?pname=waypoints
> This data is for the official route.  There are almost 2,000 waypoints for
> NM and 1700 for Colorado.  All the features detailed in the mapbooks (and
> more) are included as waypoints.
> Our New Mexico Mapbook is done.  (or nearly so - waiting for a proof right
> now)  It will be available in 1-2 weeks.   I will post here when it's
> available.
> Jerry Brown  (bearcreek)
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