[MapProxy] MBTiles shift, EPSG:3857 proj

[Oliver Tonnhofer]

On 18.09.2012, at 11:18, Fernando Ribeiro wrote:
> I have been struggling the last hours, trying to find out the origin of a small shift (around 10m NE) I detected in tiles origin on a MBTiles files generated with Tilemill. In the attached picture I overlay the shapefiles (in wgs84) used on the mbtiles file generation.

Does the shift become larger, or do you see the same pattern (no shift bottom/left, large shift top/right) for all requests?

> My MapProxy grid config looks like this:
> 
> ....
> grids:
>   GRID_SA_256_Google:
>     srs: 'EPSG:3857'   
>     bbox: [-20037508.342789236,-20037508.342789236,20037508.342789236,20037508.342789236]
>     tile_size: [256, 256]   
>     res: [156543.033928,78271.516964,39135.758482,19567.879241,9783.939621,4891.969810,2445.984905,1222.992453,611.496226,305.748113,152.874057,76.437028,38.218514,19.109257,9.554629,4.777314,2.388657,1.194329,0.597164,0.298582,0.149291]   
> 
> Is this grid valid? I googled around for the default values for Google/OSM grid specifications.


Google/OSM have a different tile origin, so you should set origin to 'nw' (north west):

 osm_grid:
    base: GLOBAL_MERCATOR
    srs: 'EPSG:3857'
    origin: nw


Regards,
Oliver

-- 
Oliver Tonnhofer    | Omniscale GmbH & Co KG    | http://omniscale.de
http://mapproxy.org | https://github.com/olt    | @oltonn