[Tagging] Way beneath overhanging cliff

[Bill Ricker]

> > Nominally layer=0 is 'ground level'. In these situations the 'ground
> level'
>
> folds back on itself - so both 'layers' are nominally 0.
>

​I think Kevin has adequately refuted that:
​

> OK, yeah, I forgot 'layer' - and I think I'd use the rule, if you look up
> to
> the zenith and see rock, you're at a layer less than zero.
>

​Hmm. I like that.
Yes, level=-1 for the lower level trail sounds better than level=+1 for the
upper here, unlike artificially elevated ways.

(reminds me of arcsine, catastrophe theory, and other math funtions of
multiple sheets.:-)
​
This obviously doesn't qualify as a tunnel since the ?north? side is open
to air; nor is it a cave, quite.  Do we have a way attribute or area
attribute for  undercut/overhang area ?

And, yeah, 'natural=cliff' is on the "to do" list. I've only recently
> started adding those, since when I render my own maps, I use
> contour lines from NED. ("Cliff" is still nice to have, since
> topographic features lurk in between the contours.)
>

​​Yes please.
The contours in Cycle Map rendering do not suggest a cliff in your original
linked location,  although  name "Escarpment Trail" does hint at it. (But
all too often, a trail is named for an *endpoint* not the view on the way,
so should be at best inconclusive.  :-)
​

Re old-school transit etc - yes, packing serious surveying gear (either
antique theodolite or modern computer/laser "total station") into the
boonies requires ​packmules, grad students, or Scouts you can pay in beef
stew, as well as a qualified operator. I'm trying to recruit some of same
for an educational, non-mapping project ...
   OTOH, a non-survey "construction-grade"  100' tape measure or rolling
wheel and either an orienteering (infantry) compass or a Boonton  "pocket
transit" (engineers/geologists) compass might be adequate to measure
heading of trail at vertical occlusion, bearing and distance along trail
from a point with good GPS posit to each occlusion point, and then to
inflection node under cover and distance between, to improve your level=-1
track.
   Alternatively, you can hunker-down with a good GPS (advanced user modes)
at each angle of the occluded trail, switch to Constellation view, and wait
until the GPS constellation gets lopsided into the narrow wedge of sky you
*can* see from there and get your best posit then. Quality will still be
low due to short baseline in sky but will be better.
​   Or try both ...

-
​73​
-
Bill
​n1vux
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/tagging/attachments/20171003/982ba690/attachment.html>