Setting up DEM editing

On the Settings tab in the DEM Editing window, you define special values that affect how you edit digital elevation models (DEM) in a session, including the Failed value and the Background value. You can also define values for filters used to convert a digital surface model (DSM) to a digital terrain model (DTM).

Another feature on the Settings tab is the Enable Smart GeoFill Special Settings check box. Select this check box when you want to copy pixels from an orthorectified image, or ortho, that you used to generate the DEM and paste those pixels into your existing mosaic. With the Enable Smart GeoFill Special Settings check box selected, your previewed ortho will have crisper edges on linear features, such as bridges. Each ortho for the area defined with the Define Preview Region command will also be regenerated. This provides a wider choice of images, each from varying angles.

Note: Applying the Smart GeoFill special settings can significantly increase the amount of time it takes to create a one-to-one ortho preview. This is due to the greater amount of data processing required to produce a full-resolution preview.

By entering a value in the 1:1 Pixel Size box, you can generate orthos to view at the specified resolution in the Full Res. Ortho Preview window.

Under Terrain filter special values, you can enter one or more values to better suit DEMs with particular issues. For example, sometimes when a surface feature is removed, small bumps remain in the surrounding area. By specifying a value in the Bumps box, you can filter out any bumps that occur.

The specified value determines how aggressively features are removed from the area inside the polygon mask. While you can use the default values, you can also enter higher or lower values, as applicable. In flat areas, especially flat urban areas, large values can be used; however, in rough terrain, use smaller values to ensure that significant natural features are not lost.

To set up DEM editing

In the DEM Editing window, click the Settings tab.
Under DEM Special Values, in the Failed box, type a value to apply to the pixels for which the generation of elevation values failed.
The failure value identifies the areas that can be interpolated and filled. This value should be outside the range of valid elevation values.
In the Background box, type the value assigned to the area that lies outside the DEM.
The background value can be a maximum or minimum value, such as -150 or -9999.

Note: If the information exists in the input-DEM metadata, these boxes are updated automatically with the available values by Focus.
Under 1:1 Preview Region Settings:
- If you want to copy pixels—in particular, sharp-edged features, such as a bridge—from orthos in the Full Res. Ortho Preview window, and paste them in the Focus viewer, select the Enable Smart GeoFill Special Settings check box.
- If you want to generate the orthos to view at a specific resolution in the Full Res. Ortho Preview window, type the resolution you want in the 1:1 Pixel Size box.
  The resolution is in the same units as the coordinate system of the orthorectified image.
Under Terrain filter special values, beside Erosion size, type a value in the Flat box, the Rough box, or the Bump box, as applicable.