<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Enzo,<div><br></div><div>Yes you would use the Buffer function in PostGIS but you can create them dynamically in your select statement within your mapnik xml mapfile, so there is no need to pre-calculate in another geometry field unless you need a speed bump. As of r769 in svn trunk, mapnik's PostGIS plugin can support multiple geometry fields.</div><div><br></div><div>For more info consider posting to the mapnik-users list and reading: <a href="http://trac.mapnik.org/wiki/PostGIS">http://trac.mapnik.org/wiki/PostGIS</a></div><div><br></div><div>Dane</div><div><br><div><div>On Jan 6, 2009, at 6:45 PM, Enzo Losantas wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">Just a minor follow up, does this mean that im going to add another column in my database,<br>use postgis to add shapefiles or buffers, then use mapnik and render the circles properly with <br>the LineSymbolizer and PolygonSymbolizer?<br> <br>Thanks, <br>Enzo<br><br><div class="gmail_quote">On Tue, Jan 6, 2009 at 5:13 PM, Enzo Losantas <span dir="ltr"><<a href="mailto:joselorenzo@gmail.com">joselorenzo@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> Anyone knowledgeable on how to go about this?<br><br>Dane, i was thinking of maybe going about this with a buffer maybe?<br>If i have a point, then i could use that point as the center of the buffer,<br>then this buffer can be the circle that i am looking for. there seems to be a <br> buffer function that postgis offers.. is that correct?<br><br>Thanks,<br>Enzo<br><br>----<br>Date: Sun, 16 Nov 2008 21:15:43 -0800<br> From: Dane Springmeyer <<a href="mailto:blake@hailmail.net" target="_blank">blake@hailmail.net</a>><br> Subject: Re: [<span>OSM</span>-dev] help: drawing <span>circles</span> on mapnik<br> To: Enzo Losantas <<a href="mailto:joselorenzo@gmail.com" target="_blank">joselorenzo@gmail.com</a>><br> Cc: <a href="mailto:dev@openstreetmap.org" target="_blank">dev@openstreetmap.org</a><br> Message-ID: <<a href="mailto:8B247371-31C0-467F-BD98-ECDCD462F9AF@hailmail.net" target="_blank">8B247371-31C0-467F-BD98-ECDCD462F9AF@hailmail.net</a>><br> Content-Type: text/plain; charset="us-ascii"<br> <br> Hi Enzo,<br> <br> I'd second Andy's recommendation of using PostGIS to render <span>circles</span><br> with varying size based on some attribute. That sounds like the right<br> place to start.<br> <br> As far as styling the <span>circles</span> once you've created them can find more<br> about the LineSymbolizer (which you can use to define the outline size<br> and color of the circle), and the PolygonSymbolizer (to define the<br> fill color) on the Mapnik wiki:<br> <br> <a href="http://trac.mapnik.org/wiki/LineSymbolizer" target="_blank">http://trac.mapnik.org/wiki/LineSymbolizer</a><br> <a href="http://trac.mapnik.org/wiki/PolygonSymbolizer" target="_blank">http://trac.mapnik.org/wiki/PolygonSymbolizer</a><br> <br> Also at the wiki is a page that has started to document some usage<br> specific to PostGIS:<br> <br> <a href="http://trac.mapnik.org/wiki/PostGIS#Usage" target="_blank">http://trac.mapnik.org/wiki/PostGIS#Usage</a><br> <br> And here is a sample script in python that shows buffering existing<br> polygon data into a larger polygon using PostGIS:<br> <a href="http://mapnik-utils.googlecode.com/svn/trunk/tutorials/postgis/postgis_geometry.py" target="_blank">http://mapnik-utils.googlecode.com/svn/trunk/tutorials/postgis/postgis_geometry.py</a><br> <br> You could likely borrow from some of the script ideas to approximate<br> the same effect with <span>circles</span>.<br> <br> Where these references are incomplete or unclear I'll try to answer<br> further.<br> <br> Dane<br> <br> <br> <br> <br> On Nov 16, 2008, at 7:40 PM, Enzo Losantas wrote:<br> <br> > Thanks Andy for replying.. somehow gave me an idea how it works.<br> ><br> > although there are still things that im confused about. as for the<br> > kind of <span>circles</span>, maybe <span>circles</span> that have dynamic<br> > radius based on a certain parameter. Since these are varying radii,<br> > I'll probably follow your advice regarding<br> > drawing polylines in postgis.<br> ><br> > As for the item on LineSymbolizer / PolygonSymbolizer, can you help<br> > me with this? Are there any available<br> > API or references that can be of help as well? How does this work<br> > exactly?<br> ><br> > thanks,<br> > Enzo<br> ><br> > On Wed, Nov 12, 2008 at 8:16 PM, Andy Allan <<a href="mailto:gravitystorm@gmail.com" target="_blank">gravitystorm@gmail.com</a>><br> > wrote:<br> > What kind of <span>circles</span> are you looking for? If you just want small<br> > <span>circles</span> to mark point locations, then make a .png and use a<br> > PointSymbolizer with it. But if you're trying to vary the size of the<br> > <span>circles</span>, like for example "draw me a circle where the radius is<br> > proportional to the population of the town", then you'd be better off<br> > creating polylines in postgis (or shapefile) and then just<br> > LineSymbolizer / PolygonSymbolizer depending on whether you want the<br> > outline or it filled.<br> ><br> > Cheers,<br> > Andy<br> ><br> > On Wed, Nov 12, 2008 at 2:54 AM, Enzo Losantas<br> > <<a href="mailto:joselorenzo@gmail.com" target="_blank">joselorenzo@gmail.com</a>> wrote:<br> > > hello,<br> > ><br> > > im wondering if anyone here is familiar with rendering <span>osm</span> through<br> > mapnik?<br> > > Particularly, anyone knows how to render <span>circles</span>? is it through<br> > node-ways or<br> > > it can be done through the rules?<br> </blockquote></div><br><br clear="all"><br>-- <br>Check these out: <br> <br> <a href="http://ohm.ecce.admu.edu.ph/">http://ohm.ecce.admu.edu.ph/</a><br><br> <a href="http://smart.com.ph/">http://smart.com.ph/</a><br> </blockquote></div><br></div></body></html>