[pct-l] Trail Mileage

[david booth]

> I suspect a couple of factors at work here (at least a couple).   
> One is
> whether the Topo software factors in uphill/downhill distance, or  
> is looking
> at it "as a crow flies the plot".   Another is just that inevitably  
> the
> track-built-from-waypoints is going to be a series of straightline  
> segments,
> approximating but never fully conforming to all the twists and  
> turns of the
> trail.

Brian,
you have really opened a can of worms here.
I may be wrong but, IMHO, GPS distance measurements are 2D not 3D and  
don't take the up and downs into account. Same as scaling with a map  
measuring wheel. The only maps I have seen that are not scaled are  
Tom Harrison maps. His trail distances are more like those that you  
would get if you walked the trail with a full size measuring wheel.  
He calls them "trail approx. mileage between points." Perhaps some  
expert can confirm this and explain further what the guide book uses,  
I suspect it is done with a map wheel in the cabin not on the trail.
Aussie Dave
Canberra Australia