The DEM Extraction Module provides a stand-alone tool that enables you to build epipolar images from a stereo pair. The Build Epipolar Images menu item is accessed by selecting Topographic > DEM Extraction > Build Epipolar Images from the Toolbox. Use this menu option to create epipolar image pairs that can be used for DEM extraction or viewed with the Epipolar 3D Cursor Tool.

  1. From the Toolbox, select Terrain > DEM Extraction > Build Epipolar Images. The Select Left Stereo Pair Image dialog opens.
  2. When you click OK in the Select Right Stereo Pair Image dialog, the Select Input Tie Points File dialog opens.
  3. Navigate to the directory and filename where the tie point information is stored. (See Select Stereo Tie Points for information about selecting tie points and saving them to a file.) Click Open. The Build Epipolar Images Parameters dialog opens.
  4. The Build Epipolar Images Parameters dialog allows you to select an Epipolar Reduction Factor and whether to save the output images to a file or to memory.
  5. To view the epipolar results, select Topographic > DEM Extraction > Epipolar 3D Cursor from the Toolbox, or use the Data Manager to select the Left Epipolar Image for the red band and the Right Epipolar Image for both the green and the blue bands. Load the RGB image into the display.
  6. Use anaglyph glasses to view the 3D image.

    Note: The choice of the left and right image determines whether the epipolar image is a true epipolar stereo image or the inverse epipolar stereo image. If your scene appears to have surface features inverted, such as rivers appearing on top of mountains, not in valleys between mountains, you are seeing the Inverse Stereo image.

    To correct this, re-display your epipolar images with the Right Epipolar Image in the red band and the Left Epipolar Image in the green and blue bands.

  7. To interactively collect map and elevation data from your epipolar stereo image, use the Epipolar 3D Cursor Tool.