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<div class="moz-cite-prefix">Am 17.10.2012 10:02, schrieb Igor
Brejc:<br>
</div>
<blockquote
cite="mid:CA+CKBJG5zZZ9+voy+=o=sbrzUArjfaU0YMQ5mfnWb3VKagoAOQ@mail.gmail.com"
type="cite"><br>
<br>
<div class="gmail_quote">On Wed, Oct 17, 2012 at 9:40 AM, Frederik
Ramm <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:frederik@remote.org" target="_blank">frederik@remote.org</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="im"><br>
</div>
The area of the "hole within the hole" does not require
special tagging, as it is covered by the multipolygon itself.
If you have a forest with a hole in a hole, then that hole in
a hole is forest as well.<br>
</blockquote>
<div><br>
</div>
<div>True, but you need to determine that geometrically (see my
previous answer) and then apply the tagging rules down the
"holes hierarchy".</div>
</div>
</blockquote>
Most current applications don't need to distinct between a hole in a
hole (or an "inner outer way") and a second outer way beneath the
first one, as most current applications don't care about the
topology, but on the geometry - and there it's only of interest
which parts of the canvas to fill and which not.<br>
<br>
For the topology interpretation again the interpretation of a way as
"hole in a hole" isn't helpful either, as more often you will have
different objects inside that you have to consider to be that hole
in the hole, without a multipolygon being in place.<br>
Therefore it's necessay to implement the logic Frederic described
above nevertheless.<br>
<blockquote
cite="mid:CA+CKBJG5zZZ9+voy+=o=sbrzUArjfaU0YMQ5mfnWb3VKagoAOQ@mail.gmail.com"
type="cite">
<div class="gmail_quote">
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
If you are, on the other hand, thinking of a "lake in the
middle of a meadow in the middle of a forest" situation, then
this is not "hole in a hole" - the forest has one hole which
is the meadow, and the meadow has one hole which is the lake.
You would have three ways:<br>
<br>
F - tagged as forest<br>
M - tagged as meadow<br>
L - tagged as lake<br>
<br>
and two multipolygons<br>
<br>
MP1: outer=F, inner=M<br>
MP2: outer=M, inner=L<br>
</blockquote>
<div><br>
</div>
<div>Yes, if you split it in two separate multipolygons, then
it's clear. But the problem is that Wiki does not explicitly
forbids (just recommends not to) doing it all in a single
multipolygon, quote:</div>
<div><br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><span
style="font-family:sans-serif;font-size:13px;line-height:19.200000762939453px;background-color:rgb(255,255,255)">Such
cascading is still recommended when the "island" in the
middle is something else than the area on the outside, but
where the "island" is the same stuff it can just be made a
hole in the hole.</span></blockquote>
</div>
</blockquote>
And where's the problem?<br>
The island is part of the area described by the multipolygon, as
every other outer way is, too.<br>
It can be handled exactly the same as long as you don't want to do
special stuff according to topology, but then again topology is
missing for most osm model elements, yet (or: you have to interpret
it from the geometry yourself).<br>
<br>
regards<br>
Peter<br>
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