SLD SYMBOL version 0.7.3 (2002-09-21) A "SymbolType" is an abstract type for encoding the graphical properties used to portray geographic information. Concrete symbol types are derived from this base type. A "BaseSymbol" defines the default properties of a symbol to be those of an external symbol, which will frequently be inside of an OGC symbol(izer) repository. The symbol properties given in-line override the base-symbol properties. LINE SYMBOL A LineSymbol is used to render a "stroke" along a linear geometry. A Geometry gives reference to a (the) geometry property of a feature to be used for rendering. A "Stroke" specifies the appearance of a linear geometry. It is defined in parallel with SVG strokes. The following SvgParameters may be used: "stroke" (color), "stroke-opacity", "stroke-width", "stroke-linejoin", "stroke-linecap", "stroke-dasharray", and "stroke-dashoffset". Others are not officially supported. A "SvgParameter" refers to an SVG/CSS graphical-formatting parameter. The parameter is identified using the "name" attribute and the content of the element gives the SVG/CSS-coded value. The "ParameterValueType" uses WFS-Filter expressions to give values for SLD graphic parameters. A "mixed" element-content model is used with textual substitution for values. A "GraphicFill" defines repeated-graphic filling (stippling) pattern for an area geometry. A "GraphicStroke" defines a repated-linear graphic pattern to be used for stroking a line. POLYGON SYMBOL A "PolygonSymbol" specifies the rendering of a polygon or area geometry, including its interior fill and border stroke. A "Fill" specifies the pattern for filling an area geometry. The allowed SvgParameters are: "fill" (color) and "fill-opacity". POINT SYMBOL A "PointSymbol" specifies the rendering of a "graphic symbol" at a point. A "Graphic" specifies or refers to a "graphic symbol" with inherent shape, size, and coloring. An "ExternalGraphic" gives a reference to an raster or vector graphical object, either online or inline, in an externally-defined graphic format. A "Mark" specifies a geometric shape and applies coloring to it. TEXT SYMBOL A "TextSymbol" is used to render text labels according to various graphical parameters. A "Label" specifies the textual content to be rendered. A "Font" element specifies the text font to use. The allowed SvgParameters are: "font-family", "font-style", "font-weight", and "font-size". The "LabelPlacement" specifies where and how a text label should be rendered relative to a geometry. The present mechanism is poorly aligned with CSS/SVG. A "PointPlacement" specifies how a text label should be rendered relative to a geometric point. An "AnchorPoint" identifies the location inside of a text label to use an an 'anchor' for positioning it relative to a point geometry. A "Displacement" gives X and Y offset displacements to use for rendering a text label near a point. A "LinePlacement" specifies how a text label should be rendered relative to a linear geometry. A "PerpendicularOffset" gives the perpendicular distance away from a line to draw a label. A "Halo" fills an extended area outside the glyphs of a rendered text label to make the label easier to read over a background. RASTER SYMBOL A "RasterSymbol" is used to specify the rendering of raster/matrix-coverage data (e.g., satellite images, DEMs). "ChannelSelection" specifies the false-color channel selection for a multi-spectral raster source. "OverlapBehavior" tells a system how to behave when multiple raster images in a layer overlap each other, for example with satellite-image scenes. A "ColorMap" defines either the colors of a pallet-type raster source or the mapping of numeric pixel values to colors. "ContrastEnhancement" defines the 'stretching' of contrast for a channel of a false-color image or for a whole grey/color image. Contrast enhancement is used to make ground features in images more visible. "ShadedRelief" specifies the application of relief shading (or "hill shading") to a DEM raster to give it somewhat of a three-dimensional effect and to make elevation changes more visible. "ImageOutline" specifies how individual source rasters in a multi-raster set (such as a set of satellite-image scenes) should be outlined to make the individual-image locations visible. MAPPED-COLOR SYMBOL (Choropleth) A "MappedColorSymbol" is used to specify the mapping of colors to ranges of values of a control variable/expression. The MappedColorSubSymbol identifies the the symbol to which to apply computed colors. The computed color is used as the 'default color' in the sub-symbol. The "matchTo" attribute tells whether to match the lookup value to the "quantity" or "label" attributes of the 'choropleth' ColorMap.