# problem with tilemill #96

Closed
opened this Issue Aug 28, 2011 · 4 comments

None yet

### 3 participants

commented Aug 28, 2011
 don't know if the problem is about polymaps or tilemill. When exporting mbtiles from tilemill and showing them in polymaps. The tiles seem having a wrong Y and then displaying a weird map. Maybe it is a parameter problem but didn't find any that will display the map correctly. https://skitch.com/taniki/fwpc5/media-food-security-africa-8-1
Contributor
 Polymaps usually uses X and Y tile coordinates starting at the top left (north west). TileMill currently uses TMS coordinates which start at the bottom left (south west). Here's a good explanation: http://alastaira.wordpress.com/2011/07/06/converting-tms-tile-coordinates-to-googlebingosm-tile-coordinates/ Specifically, to convert back and forth between TMS and polymaps coordinates, you need only flip the y axis: var ymax = 1 << zoom; var y = ymax - y - 1;
closed this Aug 28, 2011
commented Aug 28, 2011
 Thanks ! Just understood by reading the tilestach examples and the mbtiles specifications. I wrote the little function to produce the url, is it interesting for the polymaps doc or something else ? function tilestream(template) { /** Formats the specified number per TileStache. */ return function(c) { var max = 1 << c.zoom; var column = c.column % max; if (column < 0) column += max; var row = max - c.row - 1; return template.replace(/{(.)}/g, function(s, v) { switch (v) { case "Z": return c.zoom; case "X": return column; case "Y": return row; } return v; }); }; }
commented Aug 28, 2011
 @taniki Are you using TileStream for serving those tiles? You can just replace /1.0.0/ in the URL with /2.0.0/ and you won't need to convert any of the coordinates - TileStream serves tiles as XYZ from the /2.0.0/ endpoint.
commented Aug 28, 2011
 ow ... yep using tilestream. am i dumb or is it nowhere on the net ? thanks for the tips (: