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What is a Tile Service?

We are starting to see implementations of servers that are "something" like a web map server. What is that something?

  • view of the world split up into tiles
  • tiles avaiable in a single projection
  • tiles available at known zoom levels

There are a number of these servers available:

  • Nasa World Wind
  • Virtual Earth
  • OSGeo Tile Map Service
  • WMS Tile Profile
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Servers

...

So what does this client interface going to look like:

  • TileService - a good name, describes what we have
    • Configure with a single URL
    • deleage to TileServer strategy objects (one implementation per service type)
  • GeoResource
    • configured with a single URI
  • GeoResourceInfo describing the service
    • TileInfo extension descrbing zoom levels (and anything else needed)

TileServer API

Represents a single tile server, actual protocol negotiated by TileStrategy object.

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The following implementations are desired:

  • PassthroughTileCache - The initial implementaion can be virtual, and just create a standalone TileRange
  • MemoryTileCache - uses memory up to a specified capacity
  • DiskTileCache - uses diskspace up to a specified capacity

The most common compound request is handled with a special data structure, a progress monitor
is used to provide feedback on during the loadTile process, the getTiles method will return a set
of the correct size; although some GridCoverages may be transparent (or pixelated) during the loading
process.

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