[at-l] GPS vs wheel mileage

[wdlists at optonline.net (Walt Daniels)]

A wheel actually follows the terrain much closer than any DEM data. It
bounces along each rock. On the rocky trails the mileage you get is more
indicative of the how hard (or slow) you will go so that then you estimate
time from miles you come closer. 

> -----Original Message-----
> From: Jim Bullard [mailto:jbullar1@twcny.rr.com] 
> Sent: Wednesday, October 19, 2005 9:54 PM
> To: Nightwalker; Walt Daniels; at-l@mailman.backcountry.net
> Subject: Re: [at-l] re: Pittsburg(h)
> 
> At 08:05 PM 10/19/2005 -0400, Nightwalker wrote:
> > > GPS calculates mileage as a straight line between the 
> points checked 
> > > as in:
> > >
> > > Point 1 __________________________________________ Point 2
> > >
> > > But we all know the actual footpath is more like:
> > >
> > > Point 1 _/\-_/\__/U\~~/>-<\__/\-_/\__/U\~~/>-<\__- Point 2
> > >
> > > _______________________________________________
> >See my answer to Walt as to how to fix that problem.
> Which was:
> >I export my 2-second track files, long and lat only, and export the 
> >underlying elevation from the mapping program. The 
> differences are much 
> >less than 1%.
> 
> My point being that the ups and downs are more frequent than 
> the intervals on a topo map would indicate even if you take 
> them into account.
> 
>