Tiling

From OSGeo
Revision as of 22:19, 12 September 2010 by Sholl (talk | contribs) (Added GFI)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to navigation Jump to search

This page belongs to the tiling mailinglist which has been initiated after the Foss4g 2010 BoF on tiling. At the BoF it became clear that there is a need for more advanced cache management in the various tile-cache programs.

Problems

  • Tiling produces too many files to handle
  • There is need for usage-statistics on tiles
  • A smarter way for seeding is needed
  • A smarter way for deleting tiles is needed
  • GetFeatureInfo is needed (mainly bypass the requst to the backend)

Possible solutions

GeoWebCache uses a paging algorithm to manage the statistics of the tiles. Tiles are grouped in page-files and the deeper the zoomlevel the more files are in the page file. Usage statistics are handled at the page-file level, not per tile.

OSM uses special PNG files where 8x8 tiles are grouped with a special header to locate the individual tiles. This way the number of files are reduced. It is not clear of 8x8 is optimal.

Empty/single color tiles should be recognised and linked to one file. Mapproxy uses a color lookup algorithm to check if there is only one color per tile.

Use polygons as input for tileseeding.

To optimise I/O on the mapserver, use depth traversing tileseeding.