You can clip an image (raster) in ArcGIS by interactively drawing a polygon on the raster dataset within the map view to define the clipping extent. Here's how:
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Start Editing: Ensure you are in an editing session.
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Create Clipping Polygon:
- In the editing toolbar, click the "Create Features" button.
- In the Create Features pane, find the feature class you want to use to create the clipping polygon (typically a polygon feature class within your geodatabase).
- Choose the "Polygon" construction tool. Your cursor will change to allow you to digitize a polygon on the map.
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Digitize the Polygon:
- Click on the map to create the vertices of your desired clipping polygon. Make sure the area you want to keep is inside the polygon.
- Double-click to complete the polygon. This creates the clipping boundary.
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Use the "Clip" Geoprocessing Tool:
- Open the "Clip" geoprocessing tool. You can find it by searching in the Geoprocessing pane (Analysis > Tools > Clip).
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Configure the Clip Tool:
- Input Raster: Specify the image (raster dataset) you want to clip.
- Output Raster Dataset: Specify the name and location where the clipped raster will be saved.
- Clipping Geometry: Set this to "Clipping Geometry."
- Input Features (Optional): While this input is optional, if your clipping polygon is already an existing feature (rather than one you just interactively drew), you can specify the feature class containing the clipping polygon here. However, since you're interactively drawing, leave this blank in this case.
- Maintain Clipping Extent: (Optional) Specifies whether to maintain the clipping extent. Choose as needed for your project.
- NoData Value: (Optional) Sets the NoData value for the new raster
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Run the Tool: Click the "Run" button. The tool will execute, and a new, clipped raster dataset will be created at the location you specified. Only the portion of the original image within the digitized polygon will be present in the output.
Important Considerations:
- Coordinate System: Ensure that the coordinate system of your data frame (map) and raster dataset are consistent. If they are not, you may need to project your raster dataset before clipping.
- Polygon Accuracy: The accuracy of your clipping will depend on the accuracy of the polygon you digitize. Zoom in to ensure precise placement of vertices if necessary.
- Processing Time: Clipping large raster datasets can be time-consuming.
