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I have a single polygon in a local projection system. I would like to convert that polygon into an image that can be used as an overlay on google maps. I understand that it may be better to use existing projects such as Mapnik, but I am still interested in the process of turning coordinates into pixels.

My scripts current flow is as follows:

  • Convert polygons to Google Spherical Mercator Projection.
  • Divide the coordinates by the map resolution (metres per pixel) for the zoom level in question.
  • Transform the coordinates of the polygon to be relative to the origin of the image.
  • Render the coordinates to an image file.

Will such a process result in a cartographically correct rendering of the data? Am I leaving anything out?

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This might be useful - maptiler.org/google-maps-coordinates-tile-bounds-projection –  Mapperz Jul 12 '11 at 14:40
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