In WMS cache systems, metatiling consists on requesting larger tiles than ‘regular’ tile size – for us, 256×256 pixels -, and then splitting them into tiles of regular size. TileCache has this feature, and it can be used to dramatically speed up the WMS cache seeding process.
In the first section we will see how to enable TileCache metatiling in a Debian server. In the second section we will see a benchmark showing that speed up in the seeding process, and a simple method to get the best metatile size. Finally, in the third section we see how to avoid two frequent errors when using an instance of MapServer as Web Map Service (WMS) server.
1. Enabling metatiling
In TileCache metatiling is enabled in the configuration file – tilecache.cfg – and must be done in every layer we want to take advantage of this feature. Below a configuration file snippet is shown:
[cache] type=Disk base=/path/to/wms-cache/directory/ [municipalities] debug=yes type=WMSLayer url=http://myserver/sdi-lugo?service=WMS&transparent=true extension=png size=256,256 bbox=580000,4688000,680000,4850000 layers=municipios srs=EPSG:23029 extent_type=loose maxResolution=285 levels=10 metaTile=yes metaSize=15,15