Problem: Buffers created using the ArcMap Buffer wizard are larger than expected


Output from the ArcMap Buffer wizard may be slightly larger (up to 1.4%) than expected.


The Buffer Wizard uses four different settings to calculate buffers. The algorithm for 'Feature Set Optimized' contains an error that causes buffers at medium to large map scales to be slightly larger than expected.

For details on the options for the ArcMap Buffer wizard, see the related article below: "How does the ArcMap Buffer wizard calculate buffers, and how can I change the method that it uses?"

Solution or Workaround

This issue has been addressed in ArcGIS Version 8.1.2.

In ArcGIS 8.1, you can minimize the distortion of buffers related to coordinate systems by changing how ArcMap determines which coordinate system to use for the buffer process. You can do this with the Advanced ArcMap Settings Utility. See the related article below: "Change the processing parameters for the ArcMap Buffer wizard."

The criteria below should help you decide which setting to use if the default 'Feature set optimized coordinate system' is causing distorted buffers.

  • If the data frame corresponding to the data has an appropriate projection, use the 'Coordinate System of the data frame (output)' option.
  • If the data is stored in an appropriate coordinate system, and has a coordinate system definition, use the 'Coordinate system of the Feature Class (input)' option.
  • If you are buffering just a few features, use the 'Feature optimized' option. This option creates a temporary coordinate system for each feature being buffered. This option may take long if you buffer many features.

Related Information