The OGC Styled Layer Descriptor (SLD) standard defines a language for expressing styling of geospatial data. GeoServer uses SLD as its primary styling language.
SLD 1.0.0 is defined in the following specification:
Subsequently the functionality of SLD has been split into two specifications:
- OGC Symbology Encoding Implementation Specification, Version 1.1.0
- OGC Styled Layer Descriptor profile of the Web Map Service Implementation Specification, Version 1.1.0
GeoServer implements the SLD 1.0.0 standard, as well as some parts of the SE 1.1.0 and WMS-SLD 1.1.0 standards.
Elements of SLD
The following sections describe the SLD elements implemented in GeoServer.
The root element for an SLD is <StyledLayerDescriptor>. It contains a Layers and Styles elements which describe how a map is to be composed and styled.
Styles contain Rules and Filters to determine sets of features to be styled with specific symbology. Rules may also specify the scale range in which the feature styling is visible.
Rules contain Symbolizers to specify how features are styled. There are 5 types of symbolizers:
- PointSymbolizer, which styles features as points
- LineSymbolizer, which styles features as lines
- PolygonSymbolizer, which styles features as polygons
- TextSymbolizer, which styles text labels for features
- RasterSymbolizer, which styles raster coverages
Each symbolizer type has its own parameters to control styling.