How To: Symbolize polygon features so that boundary lines between polygons with like attribute values are dissolved
Eliminate boundaries between polygon areas with the same attribute value by using symbol level drawing in ArcMap; equivalent to using the ArcPlot DROPLINE command in ArcInfo Workstation. This achieves the same visual effect as dissolving features based on an attribute without affecting feature geometry.
Note: The content in this article pertains to ArcGIS versions 9.x. Later versions of ArcGIS may contain different functionality, as well as different names and locations for menus, commands and geoprocessing tools.
- Add the layer in table of contents in ArcMap.
- Right-click the layer and click Properties (layer properties window opens up).
- Select the Symbology tab.
- Click Categories in the Show list and click unique values.
- Click the Value Field drop-down list and select field containing same attribute value.
- Click the tab Add All Values.
- Click the Symbol column heading and click Properties for all Symbols from the pop-up menu. The Symbol Selector window opens up.
- Click Properties in the Symbol Property Editor window and click the + button in layer to add an empty symbol layer.
- Click the top symbol level and specify an outline width of zero.
- Click the small padlock symbol next to the top symbol level to unlock this level. Click the bottom symbol level.
- In Simple Fill, click the Color drop-down menu and select No Color. Click the Outline Color drop-down menu and select a color.
- Specify an outline width to be zero.
- In Layers, click the small padlock symbol next to the bottom level to lock second level.
- Click OK to close the Symbol Property Editor.
- Click OK to close the Symbol Selector.
- Click the Color Ramp drop-down menu and select a color scheme in Layer Properties window.
- Click Advanced and click Symbol Levels in Layer Properties window. The Symbol Levels window opens up.
- Check Draw this layer using the symbol levels specified below.
- Check Join for all symbols. Uncheck Merge for all symbols. Click OK.
- Click Apply and OK in Layer Property window.
- ArcGIS 9.2 Desktop Help: Working with symbol levels
- ArcGIS 10.0 Desktop Help: Dissolving polygon boundaries using symbol level drawing