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</o:shapelayout></xml><![endif]--></head><body lang=EN-GB link=blue vlink=purple><div class=WordSection1><p class=MsoNoSpacing><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>I am not sure am I in the right forum to ask the two tiling related questions here. If not, I do hope someone could redirect me to the right place/forum. <o:p></o:p></span></p><p class=MsoNoSpacing><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>As I understand the OSM raster-tiles serving system is one of the fundamental OSM services. Even the front page map (the SlippyMap and its layers) is based on this service as well as many private mapping systems. Further I understand that these tiles are pre-generated, edge aligned colour raster images in PNG format of a uniform dimension and created per zoom levels. At the same time, the OSM source data is (implicitly and apart from the attributes) in a vector format. So, at some stage the mentioned service must perform a vector-to-raster transformation and here is my first dilemma/question:<o:p></o:p></span></p><p class=MsoNoSpacing><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>1. Are you rasterizing geometry/vector objects first for a larger area and then tiling this raster image, or the contrary? First tiling the geometry/vector objects and so rasterizing these vector tiles?<o:p></o:p></span></p><p class=MsoNoSpacing><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>Next, I think I understand how the maintenance of this raster tiles database happens. When a mapper uploads a change all related tiles are marked for re-rendering. So, at an appropriate time the marked tiles are re-rendered and the users have an impression (more or less) that the updates happen on-the-fly. I could not find some more details about this marking process. So, my second dilemma/question is:<o:p></o:p></span></p><p class=MsoNoSpacing><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>2. When an object (given by a relation) has changed, do you mark all the related/coverage tiles for re-rendering or only those affected by the change?<o:p></o:p></span></p><p class=MsoNoSpacing><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>Just to be a bit more precise regarding the second question. Assume we have an area object, for example a larger lake with islands, given by a relation. Assume, a local editor will refine the object by changing just a short section of the outer polygon, or/and just to insert a new small missing island. The whole object is covered by hundreds of tiles while the actual change is covered by only a few.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;line-height:115%;font-family:"Tahoma","sans-serif"'>Thanks for the help/answers, Sandor.</span><o:p></o:p></p></div></body></html>