Resolution Based Loading Strategy

This Strategy is more complicated than the Tile Based Strategy, both in terms of ease of use and operation.

Resolutions are defined in terms of Map Units per pixel.

Each Layer has a defined maximum resolution (i.e. minimum zoom) that it can be displayed at. The Layer will only be displayed if the view area is sufficiently small that the resolution condition is met.

The order of Layers in the Map hierarchy is important. If more than one layer fulfils the rule, then the layer at the lowest level of the hierarchy will be used. This is illustrated below.

For a simple map with a single Layer Stack, as the view zooms in, we descend through the stack.

Note:

1. Because rasters are included in Layers as extra underlaid tiles, they break the uniformity of the tile grid. This prevents the Tile Based Strategy from working, and the Resolution Based Strategy must therefore be used.
2. The Resolution Based Strategy must be used if the map is created for runtime projection.