[Tilecache] cascading TileCache / WMS layers cached individually

[Pierre GIRAUD]

This sounds good and I will have a try soon.
François Van Der Biest also pointed me to the WMS Driver
(http://wiki.openaerialmap.org/Using_With_MapServer).

Thanks,
Pierre

On Thu, Apr 3, 2008 at 1:15 PM, Christopher Schmidt
<crschmidt at metacarta.com> wrote:
> On Thu, Apr 03, 2008 at 11:38:19AM +0200, Pierre GIRAUD wrote:
>  > Hello,
>  >
>  > Context :
>  >
>  >   We have a project with one OL WMS layer combining several WMS layers
>  > (coma separated layers list param in the WMS getMap service).
>  > By using MapFish layerTree widget (and OL mergeNewParams), the list of
>  > WMS layers may be changed by the user. This said, it's obvious that we
>  > can't get this OL layer cached. One can easily imagine that for 3
>  > different WMS layers, there are 4*3*2*1=24 possible combinations.
>  >
>  >   But as performance is really important, we propose to find an
>  > alternative to that.
>  >
>  > Proposal :
>  >
>  >   Each WMS layers could be cached individually and then merged by a
>  > WMS client also being a WMS server for OL.
>  >   This way, no geospatial data would be processed. Only image
>  > transformations (blending) would be required.
>
>  The way I would do this is to configure the WMS Driver (from GDAL):
>
>  "It is possible to configure a WMS Service conforming to a WMS-C cache by
>  specifying a number of overviews and specifying the 'block size' as the
>  tile size of the cache. The following example is a sample set up for a
>  19-level "Global Profile" WMS-C cache:"
>
>  http://gdal.org/frmt_wms.html has an example pointing to the Labs WMS-C
>  server.
>
>  This requires GDAL 1.5, but ensures that your requests match up exactly
>  to the tiles that TileCache wants.
>
>  I think this would fix both of your problems.
>
>  If you need help setting up such a thing, please let the list know what
>  your TileCache config looks like, and we can hack it out.
>
>  (A GDAL WMS driver is configured in the same way as most RASTER layers,
>  with the "DATA" statement pointing to the XML file on disk.)
>
>  Regards,
>  --
>  Christopher Schmidt
>  MetaCarta
>