08-KML Regionation
This documentation is no longer maintained. Please see the new GeoServer documentation at http://docs.geoserver.org
| Regionation applies to GeoServer versions 1.7.1 and later. |
What Is Regionation?
Displaying vector features on Google Earth is a very powerful way of creating nicely-styled maps. However, it is not always optimal to display all features at all times. Displaying too many features can create an unsightly map, and can adversely affect Google Earth's performance. To combat this, GeoServer's KML output includes the ability to limit features based on certain criteria. This process is known as *regionation*. Regionation is active by default when using the superoverlay KML reflector mode.
Regionation Attributes
The most important aspect of regionation is to decide how to determine which features show up more prominently than others. This can be done either by geometry, or by a specific attribute. One should choose with a geometry or attribute that best exemplifies the relative "importance" of the feature. When choosing to regionate by geometry, only the larger lines and polygons will be displayed at higher zoom levels, with smaller ones being displayed when zooming in. When regionating by an attribute, the higher value of this attribute will make the feature show up at higher zoom levels. (Choosing an attribute with a non-numeric value will have no effect, and will instead default to regionation by geometry.)
Regionation Strategies
Regionation strategies sets how to determine which features should be shown at any given time or zoom level. The five types of regionation strategies are external-sorting, native-sorting, geometry, random, and best_guess.
- external-sorting - This strategy creates a temporary auxiliary database within GeoServer. It takes slightly extra time to build the index upon first request.
- native-sorting - This strategy uses the default sorting algorithm of the backend where the data is hosted. It is faster than external-sorting, but will only work with PostGIS datastores.
- geometry - This strategy externally sorts by length (if lines) or area (if polygons).
- random - This strategy uses the existing order of the data and does not sort.
- best_guess - This is the default. When this strategy is selected, the strategy is actually determined by the type of data being operated on. If the data consists of points, the random strategy is used. If the data consists of lines or polygons, the geometry strategy is used.
In most cases, the best_guess strategy is sufficient.
Setting Regionation Parameters
Regionation strategies and attributes are featureType specific, and therefore are set in the FeatureType Edit page in the admin console. (From the welcome page, navigate to Config -> Data -> FeatureType -> Edit)
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| Regionation parameters are set on the FeatureType Edit page |
As with all FeatureType edits, when finished click Submit, then Apply, and then Save.