Introducing schematic layer properties
Any schematic diagram is displayed in a schematic layer, which is a composite layer composed of feature layers based on the schematic feature classes associated with the template on which the schematic diagram is based. Most aspects of each feature layer in the schematic layer can be controlled as any other layer through the Layer Properties dialog box: defining how to draw the layer, whether to label the layer, and so forth. This customization can be performed in ArcMap for each opened diagram and be different for each diagram. But default schematic layer properties can also be specified at the diagram template level so all schematic diagrams based on a diagram template are displayed in the same way.
The following section and the next topics detail all these aspects.
What are schematic layer properties?
The schematic layer properties are the set of layer properties specified for each feature layer that composes a schematic diagram layer, the layer drawing order, and the reference scale for the schematic layer. They are specified within ArcMap from the schematic layer and its related feature layers. The following sections detail schematic layer properties:
Layer properties related to each feature layer that composes a schematic layer
This concerns most of the aspects controlled through the standard Layer Properties dialog box in ArcMap:
- Symbology used to represent the schematic features (in one feature, categories, and so on); customizable through the Symbology tab
- Display effects controlled through the parameters on the Display tab
- Selection symbol specified on the Selection tab
- Field display properties on the Fields tab
- Labeling through the Labels tab
- Scale range on the General tab
Layer order in a schematic layer
Layer order determines how layers that compose the schematic layer are drawn on the map. This is specified on the Layers tab of the Layer Properties dialog box that opens when you right-click a schematic layer. The layer at the top of the list is drawn over those listed below it and so on, down the list.
Reference scale in a schematic layer
When the coordinate system specified for the schematic diagram is set, a reference scale can be specified on the schematic layer. Setting a reference scale "freezes" the symbol and text sizes used in the schematic layer so that the way they look at the reference scale is maintained at all scales. This causes the Zoom In 
and Zoom Out 
tools to work as physical zoom in and zoom out relative to this scale reference; that is, the symbols/labels related to the schematic features contained in the schematic diagram are magnified when using the Zoom In tool and appear smaller when using the Zoom Out tool. Setting the reference scale is done by right-clicking the schematic layer and clicking Set Diagram Reference Scale; this sets the current scale of the data as the reference scale to which all symbol and text sizes used in the schematic diagram will be made relative.
Tip:When a reference scale is set for a schematic diagram and you want to lay it out, the parameters for most of the predefined schematic layout algorithms can be specified so they are interpreted as relative units to the average of the symbol sizes used to represent the schematic nodes in the diagram. Specifying parameters in relative units is easier than in absolute units and has real meaning when there is a reference scale for the diagram.
Caution:The diagram reference scale cannot be set when the coordinate system specified for the schematic diagram is unknown.
Learn about specifying a spatial reference on a schematic diagram template