13  REST for Tiles

In some circumstances you may wish to return a static image of a portion of a map rather than a slippy map that can be zoomed and dragged (such as those built in the preceding sections). The process of specifying a tile is similar to that of building a regular map, but instead of ending the path with an optional query string (for zoom, size, centerpoint, etc.) you specify (non-optionally) the type, zoom, and coordinates as a continuation of the path.

The coordinate and zoom specification for tiles is completely different than for maps. A full explanation is beyond the scope of this document (see http://wiki.openstreetmap.org/wiki/Slippy_map_tilenames) but the basic concepts are as follows:

• A tile is a 256 _ 256 pixel image (PNG file) showing one part of a map of the entire world.
• A tile is specified as /zoom (z) /horizontal coordinate (x) /vertical coordinate (y), e.g. /8/16/32.
• Zoom subdivides the map into a grid and thereby determines how much of the world map fits into a single tile.
• Coordinates identify the horizontal and vertical location of an individual tile within the overall grid. The upper left tile always has coordinates of /0/0. The higher the zoom, the more sections the map is subdivided into, and thus the higher the maximum valid value for coordinates.
• The valid zoom range is 0-18. The higher the zoom, the higher the granularity of the grid:
  - At zoom 0, the grid is 1 by 1, and a tile includes the entire world map. The specification for the one and only tile would be /0/0/0.
  - At zoom 1, the number of subdivisions is doubled in both the horizontal and vertical dimensions, resulting in a 2 by 2 grid with four tiles total. The specification for the bottom right tile would be /1/1/1.
  - At zoom 2, the number of subdivisions is doubled again, resulting in a 4 by 4 grid with 16 tiles total. The specification for the bottom right tile would be /2/3/3.
  - At zoom 3, the number of subdivisions is doubled again, resulting in an 8 by 8 grid with 64 tiles total. The specification for the bottom right tile would be /3/7/7.
  - And so on...

Note: An alternative approach to generating a static (non-slippy) map tile, using a query string with zoom, latitude, and longitude, is the Mapfluence static Map (see /static at http://developer.urbanmapping.com/docs/mapfluence/rest/2.0/reference/tile/static-map).

The following steps illustrate how to specify a tile using a named layer (the base map is not specified so the default Mapfluence base map will be used):

1.  Start with the host, version, API key, and endpoint. Since we are making a tile rather than a map, the endpoint will be tile:

http://query.mapfluence.com/2.0/MFDOCS/tile

2.  Add a layer definition (separating each property value pair with a pipe) for a named layer, in this case the layer that shows all features of a Mapfluence map (essentially the base map, but used as a layer):

/mode=named|from=umi

3.  Add a definition of the desired zoom:

/11

4.  Add a definition of the desired coordinates:

/327/791.png

5.  Put it all together and you have the complete REST path for the tile:

http://query.mapfluence.com/2.0/MFDOCS/tile/mode=named|from=umi/11/327/791.png

To experiment with different tiles, open a browser window, paste the URL into the address field, and change the layer, zoom, and/or coordinates values. Here's the tile that is returned from the above URL:


Note: For complete details on the purpose and valid values of tile properties, both required and optional, refer to the /tile page of the Mapfluence REST API Reference at http://developer.urbanmapping.com/docs/mapfluence/rest/2.0/reference/tile/Tile.

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