[Tilecache] cascading TileCache / WMS layers cached individually
bluecarto at gmail.com
Thu Apr 3 07:52:27 EDT 2008
This sounds good and I will have a try soon.
François Van Der Biest also pointed me to the WMS Driver
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
> 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.)
> Christopher Schmidt
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