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<div class="moz-cite-prefix">On 2012-12-17 22:16, Martin
Koppenhoefer wrote :<br>
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<div class="gmail_quote">2012/12/17 A.Pirard.Papou <span
dir="ltr"><<a moz-do-not-send="true"
href="mailto:A.Pirard.Papou@gmail.com" target="_blank">A.Pirard.Papou@gmail.com</a>></span><br>
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<div>A level is an altitude. A layer is a drawing opacity.
Although OSM does not tag for the renderer, it uses the
tag <b>layer=*</b>. It defines <b>layer</b> as the
relative "position" (is that "altitude"?)</div>
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<div><br>
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<div>no, it is not altitude (height over ground), it is the
relative position (relative to other objects at the same
spot).</div>
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Altitude is not height over ground but above sea level.<br>
I am of course speaking of relative altitude.<br>
Position is an improper term as it applied to all directions.<br>
We badly need precision.<br>
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<div>. In fact, the only effect of assigning a layer is that
upper layer objects hide lower layer ones (it's not a
"mind your step" warning ;-))<br>
<br>
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<div>it is a way to describe in the database which object is
above which or whether they are at the same level.</div>
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Agreed. And this is why I said that the tag should be called level.<br>
Transforming that into layers is a renderer's matter that is
strictly forbidden to speak about. Yet...<br>
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<blockquote class="gmail_quote" style="margin:0 0 0
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<div text="#000000" bgcolor="#FFFFFF">I have traced lengths of
streams <br>
<ul>
<li>stream as a constant layer=-2 way, uninterrupted end
to end (even if they "don't look so deep"),<br>
</li>
<li>roads are at level 0 <br>
</li>
<li>and bridges and culverts at level -1, in the manner
mentioned above.</li>
</ul>
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<div>very strange way of mapping IMHO, how did you come to this
idea?</div>
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Exactly as you say above. They are the actual relative levels of
these objects.<br>
I have never seen a bridge sitting on a road (and hiding it, even
just as a hint).<br>
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<div> Is there a page in the wiki which encourages this style?</div>
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No but their should according to what both of us say about levels.<br>
<br>
Respectfully, I have only tagged streams that way because it doesn't
hurt anything and it's superb.<br>
<br>
When I don't agree with some way of tagging, I just don't tag.<br>
It's well enough having been accused of badly tagging boundaries
when I only continued tagging the same way they were being tagged
and it's done all over the world I investigated.<br>
Strange thanks. I simply stopped tagging boundaries.<br>
<br>
Cheers, <br>
<br>
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<td valign="top">André.</td>
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