<div dir="ltr"><div class="gmail_default" style="font-family:georgia,serif"><br></div><div class="gmail_extra"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><span class="gmail-">> Nominally layer=0 is 'ground level'. In these situations the 'ground level'</span><br></blockquote><span class="gmail-"></span><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><span class="gmail-">
> folds back on itself - so both 'layers' are nominally 0.<br></span></blockquote><div><br></div><div style="font-family:georgia,serif" class="gmail_default">I think Kevin has adequately refuted that:</div><div style="font-family:georgia,serif" class="gmail_default"><span class="gmail-"></span><br><span class="gmail-"></span></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><span class="gmail-">
</span>OK, yeah, I forgot 'layer' - and I think I'd use the rule, if you look up to<br>
the zenith and see rock, you're at a layer less than zero.<br></blockquote><div><br></div><div style="font-family:georgia,serif" class="gmail_default">Hmm. I like that. <br></div><div style="font-family:georgia,serif" class="gmail_default">Yes, level=-1 for the lower level trail sounds better than level=+1 for the upper here, unlike artificially elevated ways.</div><div style="font-family:georgia,serif" class="gmail_default"><br></div><div style="font-family:georgia,serif" class="gmail_default">(reminds me of arcsine, catastrophe theory, and other math funtions of multiple sheets.:-)<br></div><div style="font-family:georgia,serif" class="gmail_default"></div><div style="font-family:georgia,serif" class="gmail_default">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 ? <br></div><div style="font-family:georgia,serif" class="gmail_default"><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
And, yeah, 'natural=cliff' is on the "to do" list. I've only recently<br>
started adding those, since when I render my own maps, I use<br>
contour lines from NED. ("Cliff" is still nice to have, since<br>
topographic features lurk in between the contours.)<br>
</blockquote></div></div><div class="gmail_extra"><br></div><div class="gmail_extra"><div style="font-family:georgia,serif" class="gmail_default">Yes please. <br></div><div style="font-family:georgia,serif" class="gmail_default"> 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. :-) <br></div></div><div class="gmail_extra"><div style="font-family:georgia,serif" class="gmail_default"></div><div style="font-family:georgia,serif" class="gmail_default"><br></div><div style="font-family:georgia,serif" class="gmail_default">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 ... <br></div><div style="font-family:georgia,serif" class="gmail_default"> 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. <br></div><div style="font-family:georgia,serif" class="gmail_default"> 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.<br></div><div style="font-family:georgia,serif" class="gmail_default"> Or try both ...<br></div><br>-<div style="font-family:georgia,serif;display:inline" class="gmail_default">73</div>- <br><div class="gmail_signature"><div dir="ltr">Bill <div style="font-family:georgia,serif;display:inline" class="gmail_default">n1vux</div></div></div>
</div></div>