With the control provided by geometric effects and marker placement styles, representations can be used to create intelligent symbols to solve some common challenges in cartographic symbology.
For more information, visit the Mapping Center and the ArcGIS Resource Center.
Synchronizing dashes on polygon outlines
One common challenge in symbology is where multiple features share a common edge and the outlines for the features do not match. This situation is undesirable, and the most common solution is to convert polygons into linear features and add the new linear features into the map. The outlines of the polygon symbols are not displayed, and the symbology is provided by the linear features. The symbology of the linear features will match exactly. Although this method works, it requires extra data and additional feature layers.
Using representations achieves the same results and avoids the need for additional data and layers in the map. The goal is to have the patterns for each line or outline start and stop at the same location. Representation control points are used to indicate the start and stop locations for a dash pattern. Use either the Set Representation Control Point At Intersect or the Set Representation Control Point By Angle geoprocessing tools to add representation control points at key locations along the polygon outlines to force the placement and synchronization of dashes. Alternatively, use the Add control points geometric effect, or place representation control points manually along features that share a coincident edge or vertex.
Synchronizing markers with dashes
A common challenge in symbology is getting markers and dashes in a line symbol to match up. Representation symbology can be dynamically adjusted to fit the geometry of the feature, so it is important to make sure that all symbol levels in a representation rule are adjusted in the same manner. Achieving the desired result requires the use of geometric effects and marker placement styles.
To synchronize markers with dashes, use the Dashes geometric effect with the same settings on both the line symbol layer and the marker symbol layer. On the marker symbol layer, set the marker placement style to On line, and set the Relative to property to Line middle.
Making a dash-dot-dot line symbol
The main consideration in constructing a dash-dot-dot-style line symbol is choosing a marker that fits between two dashes, leaving room on both sides. The goal is to place multiple markers in the gap between dashes. Achieving the desired result requires the use of geometric effects and marker placement styles.
To synchronize two markers between dashes, set up a rule following these guidelines:
- On the line symbol layer, use the Dashes geometric effect with Pattern set equally (for example 5 5) and Endings set to With half pattern.
- On the marker symbol layer, add the Dashes geometric effect with the Pattern set equal to that of the line symbol layer (5 5 in this example), and the Endings set to With half gap.
- On the marker symbol layer, set the marker placement style to Along line.
- In the Along line marker placement style, set the Step property set to fit between the line gaps (for example 2 2), the Endings set to Custom, Position set to 1.5 and Offset at end set to 1.
Making a dashed dash line symbol
Placing a repeating pattern within another pattern is a handy way to construct a symbol that is otherwise too long or too complex to enter as a single pattern.
The red dashed line in the images below is added just to show how the dashed dash fits in the same space as the dash.
To achieve this style of symbol, place two consecutive Dashes geometric effects within a single line layer. The second one will apply to the dynamic geometry of the first, so it will dash the dashes.
Making a scalloped line symbol
A scalloped line can be constructed using the Wave and the Offset geometric effects. Using the Wave effect by itself produces waves with peaks and valleys (tops and bottoms), while using the Wave and Offset effects together causes the wave effect to create a wave with only peaks or tops. In the images below, the green line indicates the underlying geometry of the feature, and the blue line indicates the result of the geometric effects.