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How To: Determine the percentage of lines that fall within polygons

Summary

When features, such as lines, overlay other features in a map, like the polygon below, calculating the percentage of the feature overlaying another helps determine how much area is covered. The percentage of lines covered by polygons may be calculated to avoid extra segments in the map, or strictly for analysis purposes.


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Procedure

The instructions provided describe how to determine the percentage of lines that fall within polygons.

Option A: Use the Tabulate Intersection tool

Note: This tool requires an ArcGIS for Desktop Advanced license.
  1. In the Catalog window, navigate to System Toolboxes > Analysis Tools > Statistics > Tabulate Intersection.
  2. Set a polygon feature as the Input Zone Features.
  3. Select the Shape_Length field from the drop-down list for Zone Fields.
  4. Select the line feature as the Input Class Feature.
  5. Specify the location for the Output Table.
    Note: Ensure the Output Table is saved in a geodatabase.
  6. Click OK. A new table containing the Calculated Percentage is created.

For more information on how to use the Tabulate Intersection geoprocessing tool, refer to the following ArcMap Help topic: Tabulate Intersection.

Option B: Calculate the percentage manually

  1. Add a new field to the attribute table of the line feature class to store the full length values, using Double for the Type.
  2. Right-click the field > Calculate Geometry. Populate the field with the length values.
  3. Run the Intersect tool. To do this:
    1. Navigate to System Toolboxes > Analysis Tools > Overlay > Intersect.
    2. Add both the line features and the polygon features as Input Features.
    3. Specify the Output Feature Class.
    4. Click OK. A new feature class with new shape lengths is created.
  4. Add a new field in the output table to store the Calculated Percentage, using Double for Type.
  5. Right-click the field > Field Calculator. Calculate the percentage of lines in polygons:
([Shape_Length]/[Full_Shape_Length])*100
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