Symbols graphically describe, categorize, or rank geographic features and labels to locate them and show qualitative and quantitative relationships. They display graphical elements on a layout. Symbols can be optionally stored, managed, and shared in collections called styles.
Symbols are classified by the type of geometry they depict: point, line, polygon, and text. Each symbol type has unique characteristics and properties. Symbols are built from component symbol layers. These symbol layers are classified by their graphical structure—either marker, stroke, fill, or procedural. These layers are the building blocks of symbols; they combine to make rich graphical depictions. Text symbols are an exception—they have native properties but no component layers.
Fill symbol layers cover areal geometries with either a single solid color (solid fill symbol layer), a series of regularly spaced lines (hatched fill symbol layer), a gradation from one color to another (gradient fill symbol layer), or an image or texture (picture fill symbol layer.) Stroke symbol layers can be of type solid or picture. Marker symbol types include picture, 3D model (which are true three-dimensional objects), and shape, which are vector-based. Procedural symbol layers are only valid within point or polygon symbols in a 3D context. They are defined by rule package.
Each type of symbol layer is controlled by a series of properties. The properties appear in expandable groups in the Format Symbol mode of the Symbology pane. Symbols have at least one symbol layer, but can have more, as this table outlines:
|Symbol type||Typical symbol layers||Role|
Draw relative to the point geometry
Draw three-dimensional structure relative to point geometry when the symbol is used in a 3D context
Draw at specified locations relative to the line geometry
Draw relative to the line geometry
Draw relative to the polygon outline or within the polygon interior, dependent on the marker placement setting
Draw relative to the polygon outline
Draw relative to the polygon interior
Draw three-dimensional structure relative to polygon footprints, when the symbol is used in a 3D context
Text symbols do not contain layers
In addition to these arrangements, you can add any symbol layer to any symbol. You may encounter geometry logic errors, however, where it is not clear what symbol geometry you expect to be drawn by each layer. In these cases, a Symbol has inconsistent geometry logic warning message appears. Usually, adding effect to the layer is the best way to resolve this. Effects dynamically alter symbol geometry to create different appearances.
In some cases, an effect is added automatically to a newly added symbol layer to ensure that something logical draws. An example is adding a fill symbol layer to a point symbol. Since there isn't any polygon geometry to draw with this fill symbology, a Buffer effect is added to the fill layer. The fill symbology then draws the dynamic polygon formed by the buffer. You can configure the properties of the effect, or remove it and replace it with another one.
Basic symbol properties
In addition to the properties of symbols that come from the individual symbol layers, point, line, and polygon symbols also have a set of basic properties that relate to the symbol collectively as a whole. You access the basic symbol properties from the Properties tab in the Format Symbol mode of the Symbology pane, under the Symbol tab . You can make simple changes to a symbol here. If you have more than one symbol selected at a time—perhaps while modifying all of the symbols that draw a layer—you can only change the basic symbol properties. To access the detailed properties you must work with one symbol at a time.