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How To: Clip a grid to a specific polygon shape

Summary

Grids can be clipped to specific polygon shapes. Using an Analysis Mask, the output grid will only contain values within the extent of the specified area. The Spatial Analyst extension is required.

Procedure

  1. Add or create the desired polygon shapefile and grid data set to/in a view.
  2. Make the polygon theme active in the Table of Contents select "Convert to Grid" from the Theme menu. Give the new grid a storage location and name. When prompted add it to the view.
  3. Go to the Analysis drop down menu and select Properties.
  4. In the Analysis Properties, set this new grid theme as the Analysis Extent AND the Analysis Mask.
    Note:
    Failing to set this layer as the Analysis Extent will result in an output grid that contains a No Data "ring" extenting to the boundary of input grid.
  5. Click OK to exit the Analysis Properties Dialog.
  6. Go back to the Analysis menu and select Map Calculator.
  7. In the Map Calculator, double click on the grid that you want to clip from the Layers list.
  8. Click the Evaluate button.
  9. Examine the new grid in the View. If the output is correct, make it the active theme and then go to the Theme Menu. Select "Save Data Set". Give the new grid a name and storage location.