Removing noise from a DEM

Noise is a random occurrence of irrelevant or miscorrelated values distributed throughout a digital elevation model (DEM) that reduces its accuracy. The following procedure typically produces a satisfactory DEM; however, it is not recommended for areas containing large bodies of water, such as lakes.

Note: This procedure is applicable only to working with bitmap masks.

To remove noise from a DEM

In Focus, open the file containing the DEM you want to modify.
You may also want to load the reference data to more easily identify areas of the DEM to edit.
Ensure that all large bodies of water, such as lakes, are corrected.
For more information, see Adjusting pixel values for multiple lakes.
On the Maps tab, make sure the relevant DEM layer is selected, , and then on the Layer menu, click DEM Editing.
The DEM Editing window appears.
In the DEM Editing window, click the Edit via Bitmap tab, and then do the following:
1. In the Filtering and Interpolation list, click Remove Noise Filter.
2. Click Entire DEM, and then click Apply.
  If you want to run the filter again, click Apply; otherwise, proceed to the next step.
3. In the Filtering and Interpolation list, click Interpolate.
4. Make sure Entire DEM is selected, and then click Apply.
5. In the Filtering and Interpolation list, click Smooth DEM.
6. Click Entire DEM, and then click Apply.
  If you want to run the filter again, click Apply.
If you want to remove the contents of the layer, click Clear Layer or, to save the layer, click Save.