"Rick Warner" <
[email protected]> wrote in message
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> "David Storm" <
[email protected]> wrote in message
news:<
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>
> >
> > I suspect that the USGS routes are like those generated by DeLorme's Topo software. Topo
> > over-reports total climbing in hilly/mountainous routes by as much as 100%. I've never gotten
> > any answer from Delorme in response to my inquiries about the discrepancies. I have been told by
> > others that the reason is that the maps do not calculate elevations/gradients, etc for the roads
> > but rather for the native hills, ridges, gullies etc. That is, cuts through passes, high
> > bridges, etc, are ignored. Those discrepancies can build up on a long ride with lots of ups and
> > downs. An example is a route I laid out on Topo for a tour on a straight-forward route from
> > Seattle to Sacramento down the West Coast. Topo reports that total climbing is 93,000 feet for
> > the 1,000 mile trip!
> >
>
> The reason DeLorme overestimates elevation gain is fundamental to the way they process the data.
> DeLorme's software is vector based, and the vectors are relatively long. That means that their
> calculation of the topography crossed between point A and point B will usually calculate elevation
> changes that do not follow the road but rather cut across all sorts of topographically diverse
> features (unlike roads where the builders attempt to smooth out the terrain doing roadcuts, fill,
> etc.). The National Geographic (formerly Wildflower) Topo! software is raster based - every little
> point is separate. This makes it more difficult to draw routes; you have to trace the entire road
> or roads, whereas in DeLorme you just set endpoints and perhaps a few intermediates so it knows
> where to go. But the payoff is greater accuracy. On typical rides in the hills around where I live
> DeLorme's estimate of elevation gain is usually 30-50% greater than the equivalent estimate from
> Nat'l Geographic's software. I have much more confidence in NG's estimate than in DeLorme's.
> DeLorme has a funky autorouting routine, too. On one of the local hill rides I set the start of
> the route at the intersection where the particular road starts, the end point at the top of the
> hill on the same road, and DeLorme autoroutes along every small side road going up the hill. The
> only way to force it to route on the main road is to set 'Via' points at regular intervals (< 1/4
> mi) along the road. DeLorme's topo is nice for a quick look, but too inaccurate and bothersome for
> when I want to do actual routing - not to mention that it will not read data from my GPS, just
> load data into it.
>
> - rick warner
Totally agree re: DeLorme TopoUSA. I have version 4.0, and it consistently overestimates climbing.
I've sent their tech support a couple of emails on the subject, including newsgroup discussions of
the problem. But, they have chosen not to reply.
It's too bad...I really like their hardcopy "Atlas and Gazetteer" series of state guides. Their Topo
USA product could be good, if they would only do a better job of estimating climbing (it shouldn't
be THAT hard to build in some sort of correction factor).
As for your problems getting it to autoroute...check your "route preferences" settings. I'll bet
you've told it to show a preference for "local roads".
GG