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<DIV dir=ltr>Hi, according to the source code, the legacy option -M is using this projection:</DIV>
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<DIV dir=ltr> [PROJ_MERC] = { <BR> descr: "WGS84 Mercator", <BR> proj4text: "+proj=merc +datum=WGS84 +k=1.0 +units=m +over +no_defs", <BR> srs:3395, <BR> option: "" }</DIV>
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<DIV dir=ltr>Unlike EPSG:900913, that projection is not assuming that the Earth is a perfect sphere, therefore:</DIV>
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<DIV dir=ltr>- it seems to be cartographically more correct</DIV>
<DIV dir=ltr>- it probably needs far more computation</DIV>
<DIV dir=ltr>- the result probably differs from that of EPSG:900913 by a few meters</DIV>
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<DIV dir=ltr>Regards</DIV>
<DIV dir=ltr>Juan Lucas</DIV>
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<FONT size=2 face=Tahoma><B>De:</B> talk-bounces@openstreetmap.org en nombre de Francois Van Der Biest<BR><B>Enviado el:</B> vie 01/05/2009 17:52<BR><B>Para:</B> talk@openstreetmap.org<BR><B>Asunto:</B> [OSM-talk] osm2pgsql and proper/legacy mercator<BR></FONT><BR></DIV>
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<P><FONT size=2>Hi list,<BR><BR>osm2pgsql --help says:<BR>-m|--merc: Store data in proper spherical mercator (default)<BR>-M|--oldmerc: Store data in the legacy OSM mercator format<BR><BR>I'm wondering what's the difference between those two srs.<BR>Which one is epsg:900913 (aka epsg:3785<BR><A href="http://www.spatialreference.org/ref/epsg/3785/">http://www.spatialreference.org/ref/epsg/3785/</A>) ?<BR><BR>My experience (importing an osm dump into postgis, then exporting to<BR>shapefiles) would let me think that the "legacy OSM mercator format"<BR>is epsg:3785. So, what's the other one ?<BR><BR>Thank's,<BR>F.<BR><BR>_______________________________________________<BR>talk mailing list<BR>talk@openstreetmap.org<BR><A href="http://lists.openstreetmap.org/listinfo/talk">http://lists.openstreetmap.org/listinfo/talk</A><BR></FONT></P></DIV></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>