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</o:shapelayout></xml><![endif]--></head><body lang=DA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span lang=EN-US>Hi,<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>For performance reasons, I've (used FME to) split a large PNG into 450 small tiles, serving them with a Mapserver tileindex as a WMS service to a web solution.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Howeever, white lines appear between some of the tile rows (not all) at some scales (not all).<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>I've looked deeper into the WLD files for the individual tiles, and found that the calculations are accurate to 1/10 of a nanometer. At least if one uses all 10 decimals.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Tiles are 2254 pixels high, and (as per the WLDs below) 6138899.3169212583 - 0.0204375000 * 2254 = 6138853.2507962583 (almost equal to 6138853.2507962584)<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Which leads me to suspect that some sort of truncation goes on, yielding some sort of rounding error.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Do anyone know whether the tileindex calculations truncates any of the values in the WLD files ? And if so, by how much ?<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Cheers.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>--<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>A typical map picture with a white line can be seen via this link:<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US><a href="http://hvmgo01.hvenegaard.dk/mswms/mapserv.exe?map=odensekkgd_wms.map&LAYERS=ASSISTENS&TRANSPARENT=true&SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap&STYLES=&FORMAT=image/png&SRS=epsg:25832&BBOX=586609.80952408,6138781.1015875,586686.0222225,6138857.3142859&WIDTH=256&HEIGHT=256">http://hvmgo01.hvenegaard.dk/mswms/mapserv.exe?map=odensekkgd_wms.map&LAYERS=ASSISTENS&TRANSPARENT=true&SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap&STYLES=&FORMAT=image/png&SRS=epsg:25832&BBOX=586609.80952408,6138781.1015875,586686.0222225,6138857.3142859&WIDTH=256&HEIGHT=256</a><o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>Here's the WLD of the two tiles displayed in the picture:<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Upper tile WLD:<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>0.0204375000<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>0.0000000000<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>0.0000000000<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>-0.0204375000<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>586620.6934394070<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>6138899.3169212583<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Lower tile WLD:<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>0.0204375000<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>0.0000000000<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>0.0000000000<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>-0.0204375000<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>586620.6934394070<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>6138853.2507962584<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D;mso-fareast-language:DA'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D;mso-fareast-language:DA'>--<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D;mso-fareast-language:DA'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D;mso-fareast-language:DA'>Ps! As I wrote previously, I'm using FME to create the tiles. So I have little control over the actual coordinate and pixel values, and only specify the number of tiles I need. So manual truncation is not really a viable option.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D;mso-fareast-language:DA'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D;mso-fareast-language:DA'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='color:#1F497D;mso-fareast-language:DA'>Kind regards / Med venlig hilsen<br>Lars I. Nielsen<br>----------------------------------------------------------------<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D;mso-fareast-language:DA'>Landinspektør, Senior GIS Programmør og Konsulent<br>Hvenegaard Landinspektører A/S<br>Rugaardsvej 55, DK-5000 Odense C<br>Denmark<br>Tel. +45 6313 5050<br><a href="http://www.hvenegaard.dk/">http://www.hvenegaard.dk</a><o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>