Additional setup for NCC

When you select NCC (Normalized cross-correlation) for Extraction method, the Automatic DEM Extraction window refreshes to display additional options under DEM Extraction Options.

To complete the additional setup for NCC

In the Elevation range list, select how you want to detect the range:
- To have the minimum and maximum elevations generated automatically for each epipolar pair, click Automatic, if necessary.
  That is, Automatic is the default setting.
- To have the minimum and maximum elevations you specify apply globally for all epipolar pairs, click Explicit, and then in the Minimum (MSL) and Maximum (MSL) boxes, type values to represent the estimated elevation of the terrain in the stereo pair.
  To have OrthoEngine estimate the values, click Estimate.
  
  The minimum and maximum elevations are used to estimate the search area for the correlation. This increases the speed of the correlation and reduces errors. If the resulting DEM contains failed values on peaks or valleys, increase the range. Do not use values outside the range present in the stereo pair.
  
  Note: The default values are estimated elevations, based on the geocoded location of the active OrthoEngine project.
In the Failure value box, type the value to use to represent the failed pixels in the resulting DEM.
Entering a failure value helps you to interpolate these pixels when you edit the DEM. The default value is -100.
In the Background value box, type the value used to represent the NoData pixels in the DEM.
The NoData value identifies the pixels that are outside the overlap area in the extracted DEM so they are not mistaken for elevation values. The default value is -150.
In the DEM detail list, click the level of detail that you want in the extracted DEM:
- Extra high
- High
- Medium
- Low
For more information about DEM detail, see Understanding DEM detail and pixel sampling.
In the Terrain type list, click the type of terrain in the scenes being processed:
- Flat: gentle or flat terrain
- Hilly: hilly terrain (default)
- Mountainous: mountainous terrain
In the Output DEM channel type list, click:
- 16-bit signed to save the DEM in a 16-bit signed channel
- 32-bit real to save the DEM in a 32-bit real channel. This is the default setting.
To apply a Wallis filter to the input epipolar images before extracting the DEM, select the Apply Wallis filter check box.
The Wallis filter can be useful with data that contains desert or areas with significant shadows, such as mountainous regions or urban scenes.
If you intend to create a geocoded DEM, and use a clip region, select the Use clip region check box.
You will define the clip region when you later create the geocoded DEM
Return to extracting a DEM from epipolar pairs to complete the rest of the setup.