[Tilecache] Problem with spherical mercator at one zoom level

[Josh Livni]

Tilecache doesn't really know any details about different projections.  If
you tell it to render -360 to -50 in epsg:4326, it will try give that a
shot.  Different rendering engines might treat this request differently.
 I'd suggest trying these requests tilecache is making to your wms (mapnik?)
and seeing how it responds.

Note that with certain seed parameters, tilecache will try to pad the extent
you requested, even if that padding goes outside of the definition of what
the projection technically covers....

 -Josh


2010/1/17 Bjørn Sandvik <bjorn at thematicmapping.org>

> Hi,
>
> These are the tile bounds calculated by TileCache when pre-generating
> map tiles for zoom level 0 and 1 (world map, spherical mercator):
>
> C:\Python25\python.exe tilecache_seed.py country_labels2 0 2 -f
>
> ###### (0, 0, 0), (1, 1, 0)
>
> Cache miss: -20037508.34,-20037508.34,20037508.3384,20037508.3384,
> Tile: x: 0, y : 0, z: 0, time: 0.177000045776
> 00 (000000, 000000) = (-20037508.3400 -20037508.3400 20037508.3384
> 20037508.3384) [0.1810s : 5.461/s] 1/1
>
> Cache miss: 20037508.3384,-20037508.34,60112525.0168,20037508.3384,
> Tile: x: 1, y: 0, z: 0, time: 0.0149998664856
> 00 (000001, 000000) = (20037508.3384 -20037508.3400 60112525.0168
> 20037508.3384) [0.0160s : 9.896/s] 2/1
>
> Cache miss: -20037508.34,20037508.3384,20037508.3384,60112525.0168,
> Tile: x: 0, y: 1, z: 0, time: 0.0150001049042
> 00 (000000, 000001) = (-20037508.3400 20037508.3384 20037508.3384
> 60112525.0168) [0.0170s : 13.447/s] 3/1
>
> Cache miss: 20037508.3384,20037508.3384,60112525.0168,60112525.0168,
> Tile: x: 1, y: 1, z: 0, time: 0.0130000114441
> 00 (000001, 000001) = (20037508.3384 20037508.3384 60112525.0168
> 60112525.0168) [0.0150s : 16.591/s] 4/1
>
> ###### (0, 0, 1), (2, 2, 1)
>
> Cache miss:
> -20037508.34,-20037508.34,-0.000799998641014,-0.000799998641014,
> Tile: x: 0, y: 0, z: 1, time: 0.0699999332428
> 01 (000000, 000000) = (-20037508.3400 -20037508.3400 -0.0008 -0.0008)
> [0.0710s : 15.918/s] 1/4
>
> Cache miss:
> -0.000799998641014,-20037508.34,20037508.3384,-0.000799998641014,
> Tile: x: 1, y: 0, z: 1, time: 0.0680000782013
> 01 (000001, 000000) = (-0.0008 -20037508.3400 20037508.3384 -0.0008)
> [0.0700s : 15.580/s] 2/4
>
> Cache miss: 20037508.3384,-20037508.34,40075016.6776,-0.000799998641014,
> Tile: x: 2, y: 0, z: 1, time: 0.00799989700317
> 01 (000002, 000000) = (20037508.3384 -20037508.3400 40075016.6776
> -0.0008) [0.0090s : 17.717/s] 3/4
>
> Cache miss:
> -20037508.34,-0.000799998641014,-0.000799998641014,20037508.3384,
> Tile: x: 0, y: 1, z: 1, time: 0.0639998912811
> 01 (000000, 000001) = (-20037508.3400 -0.0008 -0.0008 20037508.3384)
> [0.0660s : 17.275/s] 4/4
>
> Cache miss:
> -0.000799998641014,-0.000799998641014,20037508.3384,20037508.3384,
> Tile: x: 1, y: 1, z: 1, time: 0.0739998817444
> 01 (000001, 000001) = (-0.0008 -0.0008 20037508.3384 20037508.3384)
> [0.0750s : 16.664/s] 5/4
>
> Cache miss: 20037508.3384,-0.000799998641014,40075016.6776,20037508.3384,
> Tile: x: 2, y: 1, z: 1, time: 0.00800013542175
> 01 (000002, 000001) = (20037508.3384 -0.0008 40075016.6776
> 20037508.3384) [0.0100s : 18.113/s] 6/4
>
> Cache miss: -20037508.34,20037508.3384,-0.000799998641014,40075016.6776,
> Tile: x: 0, y: 2, z: 1, time: 0.00899982452393
> 01 (000000, 000002) = (-20037508.3400 20037508.3384 -0.0008
> 40075016.6776) [0.0100s : 19.500/s] 7/4
>
> Cache miss: -0.000799998641014,20037508.3384,20037508.3384,40075016.6776,
> Tile:x: 1, y: 2, z: 1, time: 0.00799989700317
> 01 (000001, 000002) = (-0.0008 20037508.3384 20037508.3384
> 40075016.6776) [0.0100s : 20.794/s] 8/4
>
> Cache miss: 20037508.3384,20037508.3384,40075016.6776,40075016.6776,
> Tile: x: 2, y: 2, z: 1, time: 0.00999999046326
> 01 (000002, 000002) = (20037508.3384 20037508.3384 40075016.6776
> 40075016.6776) [0.0110s : 22.030/s] 9/4
>
> ----------------------------------------
>
> Why are several of these tiles out of bounds defined by spherical
> mercator (-20037508.34, -20037508.34, 20037508.34, 20037508.34). I've
> made a Google Spreadsheet showing the mismatch:
>
> http://spreadsheets.google.com/pub?key=tBo1PLS1uldW01SgSv3se8A&single=true&gid=0&output=html
>
> [country_labels2]
> type=Mapnik
> mapfile=C:\EarthAtlas\maps\merc_country_labels2.xml
> spherical_mercator=true
>
> Cheers,
> Bjørn
>
> http://blog.thematicmapping.org
>
>
>
> 2010/1/16 Bjørn Sandvik <bjorn at thematicmapping.org>:
> > Cross-posting from Mapnik-users:
> > https://lists.berlios.de/pipermail/mapnik-users/2010-January/002824.html
> >
> > I'm experiencing a strange error with TileCache rendering labels with
> > Mapnik and a point shapefile. For zoom level 1 only labels on the
> > southern hemisphere (the two bottom tiles) are rendered - see the
> > image attachment on the link above. The other zoom levels are rendered
> > correctly. It works when using standard latitude/longitide projection
> > (EPSG:4326), but not "spherical mercator".
> >
> > Is this an issue with TileCache?
> >
> > Cheers,
> > Bjørn
> >
> > http://blog.thematicmapping.org
> >
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>
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