The standard GetMap request returns a rendered map image for the layers you request, using a chosen coordinate system, bounding box, size, format using predefined styles that are saved on the WMS server.
Dynamic styling adds the ability to define a custom style in the request to use in place of a predefined style. The WMS service supports the following types of custom styles (called themes)
- Override theme: Applies a single style to all features in a layer. Different styles can be applied to points, lines and polygons in an override theme.
- Individual Value theme: An individual value theme references a field in the layer (numerical or string), which categorizes the data. For example, a field representing the severity of fire risk (very high, high, medium, low). The theme defines the values to use, and each feature is assigned the color, symbol, or line for its corresponding value.
- Range theme: A range theme references a numeric field present in the layer. For example, the population of a county. The theme defines the numeric ranges to use, and each feature is assigned the color, symbol, or line for its corresponding range.
For each of the themes you can define styles for point, line and area (polygon) features. You can specify different styles for each feature type.
The style is sent on a per request basis in the SLD_BODY parameter along with the other standard WMS parameters.
- The style details must be in the Precisely JSON style structure which is detailed below. Note that the Precisely style is not the same as the StyledLayerDescriptor XML document used in other WMS services.
- Both GET and POST requests are supported for the getMap request. POST requests can be used in for larger styles where the Request-URI is too large for a GET request.
- The style details must be sent in a URI-encoded format. For a GET request the style is sent as a URL encoded string as a value for the parameter SLD_BODY. For a POST request the style is sent in the SLD_BODY parameter using x-www-form-urlencoded.
- In cases where two or more layers are specified in the request URL the style details can include an array of themes, with one style per layer. In these cases each theme in the style details must also include the layer name that it relates to.