Patterned lines drawn twice for shared edges in polygon coverage

Description

The polygon coverage is built and cleaned, but shared edges still draw twice.

Cause

Even though polygon coverages have topology, the ArcGIS drawing framework does not leverage this. Each polygon is drawn separately, so any shared edges are drawn twice.

The problem appears when using cased or patterned lines.

Solution or Workaround

• For cased lines, turn on advanced drawing.
  
  Summary:
  Use the following procedure to join cased polygon outline lines. This creates a nice cartographic effect.
  
  Procedure:
  Select an option below:
  
  

  • <b> ArcGIS 8.x </b> - The first part of the procedures, steps 1 through 10, describe the creation of cased line symbols for polygon outlines.
    The second part of the procedure, steps 11 and 12, describe the use of the Advanced Drawing Options to join the cased line outlines.
    
    1. Start ArcMap and add a polygon dataset.
    
    2. Double-click on the layer's symbol in the Table of Contents.
    
    3. Click Properties in the Symbol Selector dialog box.
    
    4. Click on the Add Symbol Layer button
    in the Symbol editor, located in the lower left corner of the dialog box.
    
    5. Change the fill color of the top symbol layer to No Color.
    
    6. Change the outline color of the top symbol layer to the color of the center of the cased line surrounding the polygons.
    
    7. At the bottom left corner of the dialog box, select the bottom symbol layer to edit it.
    
    8. Change the fill color of the bottom symbol level to the color you want to fill your polygons.
    
    9. Change the outline width and color of the bottom symbol level. Make this line thicker than the outline for the top symbol level's outline.
    
    10. Click OK to close the Symbol Editor and Symbol Selector dialog boxes.
    
    11. Right-click on the data frame and select Advanced Drawing Options from the menu.
    
    12. Check 'Draw using symbol options specified below' in the Advanced Drawing Options dialog box. Click OK.
    
    
  • <b> ArcGIS 9.x </b> - The first part of the procedures, steps 1 through 11, describe the creation of cased line symbols for polygon outlines.
    The second part of the procedure, steps 11 and 12, describe how to join the cased line outlines.
    
    1. Start ArcMap and add a polygon dataset.
    
    2. Right-click on the name of the layer in the Table of Contents, and open the Layer Properties dialog from the context menu.
    
    3. In the Symbology tab, click on the colored box representing the symbology for the layer to open the Symbol Selector dialog.
    
    4. Click Properties in the Symbol Selector dialog box.
    
    5. Click on the Add Symbol Layer button
    in the Symbol editor, located in the lower left corner of the dialog box.
    
    6. Change the fill color of the top symbol layer to No Color.
    
    7. Change the outline color of the top symbol layer to the color of the center of the cased line surrounding the polygons.
    
    8. At the bottom left corner of the dialog box, select the bottom symbol layer to edit it.
    
    9. Change the fill color of the bottom symbol level to the color you want to fill your polygons.
    
    10. Change the outline width and color of the bottom symbol level. Make this line thicker than the outline for the top symbol level's outline.
    
    11. Click OK to close the Symbol Editor and Symbol Selector dialog boxes.
    
    12. Click on the Advanced > Symbol Levels button in the Symbology tab of the Layer Properties dialog to open the Symbol Levels dialog.
    
    13. Check 'Draw this layer using the symbol levels specified below'. The checkbox under Join should be checked on. Click OK to exit the Symbol Levels dialog box, and OK to exit the Layer Properties dialog.
    
    
  
  
• For patterned lines, use the arcs feature class of the coverage.