How to create and use Cartographic Representations

October 26, 2012

(ArcInfo and ArcEditor Only)
What are Representations?
Introduced at version 9.2, Representations allow users to control and manipulate the appearance of features through rules defined in individual feature classes within a geodatabase. Representation rules can create and draw dynamic geometry that differs from the feature shape, allowing a complex depiction of features without impacting the spatial integrity of your data. Representations also allow you the ability to control the appearance of features in a way that previously required exporting your map to a dedicated graphics program.
In this article, we will learn how to create Representations rules in both ArcCatalog and ArcMap. Furthermore, we will also go through the steps of using Representations rules to symbolize data, alter the geometry of a representation, as well as examining Free Representations.
Before we get started, a few things to note about Representations:
- Representations can only be created and edited with an ArcInfo or ArcEditor License, but can be viewed with an ArcView license.
- In order to create and use representations, your data must be contained within a geodatabase.
- A single feature class may have more than one Representation rule applied to it.
How to add a Representation Rule to a Feature Class:
You can add Representation rules to a feature through both ArcCatalog and ArcMap.
To add a Representation Rule in ArcCatalog:

1. In ArcCatalog, navigate to the feature class in the Catalog Tree. Your data must be contained within a Geodatabase.
2. Right-click the name of the feature class and choose Properties.
3. Click the Representations tab.
4. Click New to open the New Representation dialog box.
5. Type a name for the new feature class representation and names for the RuleID and Override fields or accept the default names.
   Note: Two fields, by default called RuleID and Override are appended to a feature class each time a representation is added. The RuleID field associates a representation rule to each feature, while Override holds feature specific exceptions to representation rules. This will be discussed further in this document.
6. Decide the method you want to use to store changes to geometry:
   • Choose Store change to geometry as representation override to place all modifications to feature representation geometry in the Override field, leaving the Shape field intact.
   • Select Change the geometry of the supporting feature to force edits made to the feature representation geometry to also alter the geometry of the source feature.
7. Choose whether or not to import from an existing layer that symbolizes features with a representation.
8. If yes, click ‘Select' to navigate to the layer on the Select a Feature Layer dialog box; then click Select to close the dialog box and return to the New Representation dialog box.
   All the representation rules of that layer will be copied into this feature class representation.
9. If the layer specified in the previous step is based on the same feature class as this feature class, you can also choose to assign the representation rules to features by checking the Assign rules to features to match the layer checkbox. If you are importing representation rules originating from a different feature class, this option will be disabled.
10. Click Next.
11. Modify the representation rule structure if necessary.
    This can also be done later in ArcMap using the Symbology tab on the Layer Properties dialog box. We will go through this in greater detail later in this article.
12. Click Finish to close the dialog box.
    The new feature class representation will be listed on the Representation tab of the Feature Class Properties dialog box.

To add a Representation Rule in ArcMap:
When creating a representation rule in ArcMap, the method in which the data is currently symbolized will be used to symbolize the newly created representation. After completion a new layer in the Table of contents containing the Representation will be added.

1. In ArcMap, right-click the layer in the table of contents.
2. Click Convert Symbology to Representation.
   The Convert Symbology to Representation dialog box appears:
   
3. Type the name of the new feature class representation or accept the default name.
4. Type the names of the RuleID and the Override fields or accept the defaults.
5. Decide how edits to feature representation geometry will be stored.
   • Choose Store change to geometry as representation override to place all modifications to feature representation geometry in the Override field, leaving the Shape field intact.
   • Select Change the geometry of the supporting feature to force edits made to the feature representation geometry to also alter the geometry of the source feature.
6. Decide if you want to convert all the features in the feature class or only those that are visible in the current extent.
7. Decide whether or not to add the new feature class representation to the current map. The original layer will still appear in the table of contents regardless of your choice.
8. Click Convert. A new feature class representation is added to the source feature class, populated with representation rules that correspond to the appearance of the symbols used in the original layer.

Using Representations:

Once you have created you Representation, you can use the Symbology Tab in ArcMap or the Representation Properties in ArcCatalog to modify the Symbology of your rules:

Editing a Representation rule in ArcMap:

• Right click your Representation feature in the Table of Contents
• Properties
• Symbology tab
• Select Representations in the list on the left hand side
• Select the Rule (By default Rule_1) that you would like to modify

We can now modify the colour and characteristics of the representation rule
Important to Know!
There are three symbol layer types:
Fill symbol layers symbolize polygon geometry with one of three patterns:

• Solid—Fills polygons uniformly with a single color
• Hatch—Covers polygons with evenly spaced parallel lines
• Gradient—Fills polygons with a smooth transition between two colors in a linear, circular, or rectangular shape or a buffer that follows the contour of the polygon boundary

Stroke symbol layers symbolize line geometry and polygon outlines with a solid stroke. They are defined by color, line width, cap type, and join type.
Marker symbol layers symbolize points or locations with a representation marker symbol. Representation markers can be a collection of multiple geometry types grouped together into a single graphic symbol.
We can use Marker, Stroke or Fill symbols to symbolize data that is not a polygon, point or line.
For example, we can symbolize the WetlandsA layer which is a polygon feature class with both a fill symbol (for a polygon feature) and a Marker Symbol (for a point feature).

To perform this:

• In the Representations tab, select ‘Add a new marker layer' as below

• A new Marker layer will be added to this rule
• Click on the marker colour, and select an appropriate icon for the wetland. In this case, we will scroll to swamp and add this as the icon.
  
• The default method this marker is placed will be ‘Polygon center' meaning one marker will be placed at the centre of each polygon
• In this case, we would like to disperse the marker symbols throughout the polygon.
• To change the placement properties of this marker symbol within the polygon, click on the arrow in the right hand corner of the marker symbol next to where it says ‘Polygon center'. A dialog box with Marker Placement options will appear. We can change the effect to ‘Randomly inside polygon' so that the markers will be dispersed throughout the polygon.
• Change the X and Y Offset values from the default to 25, or an appropriate value. This will adjust the distance between where the markers are placed within the fill symbol.
• Flip back to the Fill symbol, and change the colour of the fill symbol from the default to a blue colour to depict the water.
  The result will be a symbology that shows wetlands using both a fill and a marker symbol:
  The above scenario is an example of both features contained in the WetlandsA dataset being symbolized by the same representation rule. This rule is setup in the Rule_ID field created when creating the representation. There are occasions where you may want a specific feature to override this rule and use its own representation. The Override field created when creating the representation will handle such instances.

How to Override a Representation Rule for a Specific Feature

In the last demonstration, when the representation rule was changed, it changed for all features in the dataset. If we wanted to change the Representation for one feature without affecting the others in the dataset, we can create what is known as an Override.

In the below example, we will look at changing the symbology of a bridge over a waterway.

Here we have an instance where we want to change the symbology and size associated with a bridge over a waterway; we perform this edit using the tools available on the Representation toolbar.
To perform this edit, the Editor and Representation toolbars need to be added to ArcMap.

• Tools Menu -> Customize -> check on Editor and Representation
• Start Editing
• On the Representation Toolbar, use the ‘Select Tool' to select the one feature you would like to modify
• On the Representation Toolbar hit the Representation Properties button Select the Rule that you would like to modify. In this demonstration, it is called ‘Class 3'
  In this case we would like to change the width of the bridge to be thicker than that of the road. We will change it from the default .1.08 to 2. After you change the width in this manner you will notice a little paintbrush icon next to the width field. This indicates that the default representation rule has been overridden. This information is stored in the Override field that was created when the representation rule was created.
  
  After completed, you can stop editing and view your changes:
  
  The bridge is now thicker than the rest of the roadway. The representation rule for the whole dataset was not overridden, but rather just the rule for this particular feature. The attributes of the feature class are not altered, just the representation.
  Overriding Geometry
  Furthermore, you can override the geometry of feature if you feel that the data is blocking another element of your map, or perhaps appears too cluttered.
  A common example of this might be geocoded addresses that appear on top of one another. Here we have an example of three points that rest almost on top of one another, and are not clearly visible. By using representations, we can move these features so that we are able to display each of these points visually, without changing the geometry of the feature.
  
  To spread these points out and change the position of them, we can do the following:
• Start Editing
• On the Representation Toolbar, use the ‘Direct Select Tool' to select the feature you would like to modify. Select each feature one by one. To do this draws a box so you see a blue square indicating that you have selected a point feature. Hover over the square until you see a little icon appear:
  Once you see the icon, you can move your feature. Repeat for the other point or points that you would like to move. The end result is that the points have been spread out making them all visible.
  
  The geometry of the feature class has not changed.
  
  Free Representations:
  There are very specific times that you may want to use a functionality known as a Free Representation. A Free Representation is the representation of a single feature that has been disconnected from its representation rule to create an independent rule whose structure can be changed, allowing full freedom of display. Essentially, you have the ability to manipulate complex features to you liking, However, Free Representations can be very time consuming and require careful attention. The choice to use free representations is made after you have answered no to the following questions:
  Does standard ArcMap symbology achieve the result I want?
  Does a representation rule help achieve the result I want?
  Do geometric effects help achieve the result I want?
  Do overrides help achieve the result I want?
  If truly desired, the following is an instance in which you may want to use a free representation: You may want to change the individual symbology of a Stream under a roadway.
  
• Start Editing
• Add the Representation Toolbar
• Make the layer you are editing the only Selectable layer by right clicking on the layer in the table of contents
• Selection
• Make This the Only Selectable Layer
  
• With the Select Tool on the Representation Toolbar , select the feature that you would like to create a free representation from.
• After selected, from the drop-down menu on the Representation toolbar, click Free Representation and click Convert to Free Representation.
  
• From the drop-down menu on the Representation toolbar, click Free Representation and click Convert Effect to Geometry.
  
• From the drop-down menu on the Representation toolbar, click Free Representation and click Ungroup Elements.
  Now you are able to select an individual dash in the stream and edit it as you desire.
• 
  On the Representation toolbar, you can use the ‘Direct select' tool to select individual features and move them as you see fit. The following shows that two individual dashes have been moved:
  

© 2013 Esri Canada. All Rights Reserved.