Cached layer

In the next step we'll configure the layer countries to apply to all needed cache-properties.

  • Go to Data ❭ Layers and select the countries layer.
  • Open the panel Tile Caching.

Here we can configure all GWC-dependend properties in a per-layer-basis. The most important configuration parameters are:

  • Create a cached layer for this layer: Should this layer be cached?
  • Metatiling factors: Metatiles are larger map tiles from which the cached tiles will be cut. The factor in this case indicates the size of the metatiles. A factor of 3x3 means that the screen width of the target tile is increased by a factor of three that results (by a requested tile size of 256px) in an metatile tile size of 768px. Primarily metatiles are needed to prevent duplicate map labels (for example for road layers) in two adjacent tiles.
  • Gutter size in pixels: Additional frame (in px) to be requested by a tile. Only useful when there are layout problems in the preparation of labels and/or features on the tile edge in conjunction with the use of metatiles.
  • Tile Image Formats: The standard image format for the tiles.
  • STYLES: Is there any other style existing for the given layer that should be cached, it must be selected here. In most cases it will be sufficient to set the default layer styles (LAYER DEFAULT) only.
  • Gridset: The gridset defines the grid the stored tiles are indexed and thus defines the spatial index of the individual tiles. The single tile in the rectangular grid is identified by means of a x, y, z coordinate triple. The x and y coordinates determine the horizontal and vertical position, the z coordinate the zoom level. See previous chapter as well.

Configure a cached layer

With this in mind, we can configure the layer countries as follows:

  • Select the following values:
    • Create a cached layer for this layer: checked
    • Enable tile caching for this layer: checked
    • Metatiling factors: 4 x 4
    • Gutter size in pixels: 0
    • Tile Image Formats: Check image/png only
    • Expire server cache after n seconds: 0
    • Expire client cache after n seconds: 0
    • Styles: Select LAYER DEFAULT
    • Gridset: Select momo-4326 in the Add grid subset combobox and click the green plus icon. Remove any other preconfigured gridset by clicking the red minus icon.

  • Click Save.