On 4/14/07, <b class="gmail_sendername">Artem Pavlenko</b> <<a href="mailto:artem@mapnik.org">artem@mapnik.org</a>> wrote:<div><span class="gmail_quote"></span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div style=""><div><br></div><br><div><span class="q"><div>On 14 Apr 2007, at 10:47, 80n wrote:</div><br><blockquote type="cite">David<br>I think there are a couple of problems with closing off the ends of the river sections.
<br><br>Firstly, purists would argue that a segment crossing the river is an artifice that does not represent anything in the real world. <br><br>Second, you would need two segments, or the segment needs to belong to two ways (the upstream way and the downstream way). If it belongs to two ways then for one of them it is pointing in the wrong direction. (segment sorting will fix that, but that requires running frollo before Osmarender).
<br><br>I've contemplated doing this myself several times and always managed to persuade myself not to.<br><br>80n<br></blockquote><div><br></div></span><div>80n,</div><div>We don't really need all this crossing segments.
</div><div>Please, could you explain to me what's wrong with representing features like 'river with islands' as proper polygons (one exterior and n-interior rings) ? If you want just a small part of a bigger polygon for rendering use _clipping_.
</div></div></div></blockquote><div><br>Artem<br>That's what I said wasn't it? There should not be segments crossing the rivers because:<br><span class="q"><br>"Firstly, purists would argue that a segment crossing
the river is an artifice that does not represent anything in the real
world. <br><br>Second, you would need two segments, or the segment
needs to belong to two ways (the upstream way and the downstream way).
If it belongs to two ways then for one of them it is pointing in the
wrong direction. (segment sorting will fix that, but that requires
running frollo before Osmarender)."</span><br><br>80n <br></div><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div style=""><div>
<div>Cheers,</div><div>Artem</div><div><span class="e" id="q_111ef8bf7f2da741_3"><div><br></div><div><br></div> <br><blockquote type="cite"><br>BTW I noticed an error on the Baghdad map. The al-Sarafiya bridge is still shown, but it was blown up last week ;)
<br><br><div><span class="gmail_quote">On 4/14/07, <b class="gmail_sendername">David Groom</b> <<a href="mailto:reviews@pacific-rim.net" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">reviews@pacific-rim.net
</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> <div bgcolor="#ffffff"> <div><font face="Arial" size="2">If the ends of the riverbank were closed off with segments so the riverbank formed a complete polygon, would the method outlined below by 80n be enough to render rivers and islands correctly in the mapnik layer?
</font></div><span> <div><font face="Arial" size="2"></font> </div> <div><font face="Arial" size="2">David</font></div></span><div><span> <blockquote style="border-left: 2px solid rgb(0, 0, 0); padding-right: 0px; padding-left: 5px; margin-left: 5px; margin-right: 0px;">
<div style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">----- Original Message ----- </div> <div style="background: rgb(228, 228, 228) none repeat scroll 0% 50%; -moz-background-clip: -moz-initial; -moz-background-origin: -moz-initial; -moz-background-inline-policy: -moz-initial; font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">
<b>From:</b> <a title="80n80n@gmail.com" href="mailto:80n80n@gmail.com" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">80n</a> </div> <div style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">
<b>To:</b> <a title="reviews@pacific-rim.net" href="mailto:reviews@pacific-rim.net" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)"> David Groom</a> </div> <div style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">
<b>Cc:</b> <a title="talk@openstreetmap.org" href="mailto:talk@openstreetmap.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)"> talk@openstreetmap.org</a> </div> <div style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">
<b>Sent:</b> Saturday, April 14, 2007 9:21 AM</div> <div style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">
<b>Subject:</b> Re: [OSM-talk] Islands </div> <div><br></div>One method that currently works is to tag islands as part of the same way as the riverbanks, but make them go anti-clockwise.<br><br>So you have one way that goes up the left bank of the river for, say, 1km then goes down the right bank for for the same distance. If the two riverbanks are imagined to be part of a closed way then the segments should point in a clockwise direction. Then all of the islands within that 1km section are also made part of that same way, but tagged in an anti-clockwise direction.
<br><br>This seems to work pretty well, even when cut at arbitrary points by a bbox, and is understood by SVG so renders with Osmarender. The same principle also workd for islands in lakes and any other situation where something has a "hole" in it.
<br><br>There are some examples along the River Thames:<br><br>Simple example: <a href="http://www.informationfreeway.org/?lat=6698535.88756&lon=-57979.86205&zoom=16&layers=B000" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">
http://www.informationfreeway.org/?lat=6698535.88756&lon=-57979.86205&zoom=16&layers=B000 </a><br>Complex example: <a href="http://www.informationfreeway.org/?lat=6688981.2611&lon=-51110.08562&zoom=16&layers=B000" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">
http://www.informationfreeway.org/?lat=6688981.2611&lon=-51110.08562&zoom=16&layers=B000 </a><br><br>80n<br><br> <div><span class="gmail_quote">On 4/14/07, <b class="gmail_sendername">David Groom</b> <
<a href="mailto:reviews@pacific-rim.net" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">reviews@pacific-rim.net</a>> wrote:</span> <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div bgcolor="#ffffff"> <div><font face="Arial" size="2">I don't know :)</font></div> <div> <div><font face="Arial" size="2"></font> </div> <div><font face="Arial" size="2">I've been meaning to update the large rivers page [1] to get debate going on the whole large rivers / lakes idea, which would include a discussion on how to render islands.
</font></div> <div><font face="Arial" size="2"></font> </div> <div><font face="Arial" size="2">Straying away from your initial question, and looking at large rivers, Osmarender currently renders large rivers, but the Mapnik layer does not.
</font></div> <div><font face="Arial" size="2"></font> </div> <div><font face="Arial" size="2">As I understand it Mapnik needs a proper polygon to generate the fill and so does not generate a filled wide river from the proposed rendering on the large rivers [1] page.
</font><font face="Arial" size="2">Own its own this is fairly easy to implement.</font></div> <div><font face="Arial" size="2"></font> </div> <div><font face="Arial" size="2">Moving now to your question about islands :
</font></div> <div><font face="Arial" size="2"></font> </div> <div><font face="Arial" size="2">It is, as far as I can see, fairly difficult to intuitively split a river with islands in it into polygons (particularly where there are many islands close to each other) , where each polygon would be a continuous way and there is not a complicated system of segments going between the riverbank and each island.
</font> </div> <div><font face="Arial" size="2"></font> </div> <div><font face="Arial" size="2">I'd like to see a modification of my proposal on the large rivers page [1] where riverbanks would be drawn as a polygon with a tag something like waterway = riverbank, and islands in these rivers woul
</font><font face="Arial" size="2">d be drawn as waterway = riverbank; island = yes. Given this suggested rendering, island in lakes could be tagged exactly the same as islands in rivers and they would still render correctly.
</font></div> <div><font face="Arial" size="2"></font> </div> <div><font face="Arial" size="2">David</font></div> <div><font face="Arial" size="2"></font> </div> <div><font face="Arial" size="2"></font> </div>
<div><font face="Arial" size="2">[1] <a href="http://wiki.openstreetmap.org/index.php/Proposed_features/Large_rivers" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">http://wiki.openstreetmap.org/index.php/Proposed_features/Large_rivers
</a></font></div> <div><font face="Arial" size="2"></font> </div> <div><font face="Arial" size="2"></font> </div> <blockquote style="border-left: 2px solid rgb(0, 0, 0); padding-right: 0px; padding-left: 5px; margin-left: 5px; margin-right: 0px;">
<div><span> <div style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">----- Original Message -----
</div> <div style="background: rgb(228, 228, 228) none repeat scroll 0% 50%; -moz-background-clip: -moz-initial; -moz-background-origin: -moz-initial; -moz-background-inline-policy: -moz-initial; font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">
<b>From:</b> <a title="lewispusey@earthlink.net" href="mailto:lewispusey@earthlink.net" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">lewispusey</a> </div> <div style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">
<b>To:</b> <a title="talk@openstreetmap.org" href="mailto:talk@openstreetmap.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">talk@openstreetmap.org</a> </div> <div style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">
<b>Sent:</b> Friday, April 13, 2007 5:08 PM</div> <div style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">
<b>Subject:</b> [OSM-talk] Islands</div> <div><br></div> <div><font face="Arial" size="2">What is the current best way to draw and tag islands in rivers and lakes?</font></div> <div><font face="Arial" size="2">
Lewis</font></div></span></div><div><br></div> <hr><div><br></div>_______________________________________________<br>talk mailing list<br><a href="mailto:talk@openstreetmap.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">
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</a><br><div><br></div></blockquote></div></div><br>_______________________________________________<br>talk mailing list<br><a href="mailto:talk@openstreetmap.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">
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</a><br><br></blockquote></div><br><div style="margin: 0px;">_______________________________________________</div><div style="margin: 0px;">talk mailing list</div><div style="margin: 0px;"><a href="mailto:talk@openstreetmap.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">
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</a></div> </blockquote></span></div></div><span class="sg"><br><div> <span style="border-collapse: separate; border-spacing: 0px; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px;">
<div>Artem Pavlenko</div><div><a href="http://mapnik.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">http://mapnik.org</a></div><div><br></div><br></span> </div><br></span></div></blockquote></div>
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