To generate a Gray Level and Shaded Images

See about the GL/Shaded Image in the SPRING

Generating a Gray Level Image and Shaded Image:

  • check that a rectangular grid was generated for the desired information layer of the numerical category. Otherwise, when trying to access the image generation function, the following message will be displayed: "Grid in the active Information Layer was not found!";
  • activate, in the "Control Panel", the Information Layer that has the rectangular grid;
  • click on DTM, in the main menu, and select Image Generation...;
  • select the desired Image type, Gray Level or Shaded image (see what to do for each option next);
  • fill the Vmin and Vmax fields with the maximum and minimum height values to be considered in the image grid transformation, respectively. The values out of this slice will be mapped to the 0 Gray value when it is smaller than Vmin, and to 255 when it is larger than Vmax. Notice: the Vmin value has to be smaller than Vmax value.
  • click on Output Category... and use the dialog box "Categories" to select a category from the Image model which will be associated to the output IL. After selecting the category, click on Apply in this window;
  • type the Output Layer name;
  • set number of bits for the Output image;
  • For a Gray Level Image:   just  click on Apply to create a Gray level image;
  • For a Shaded Image, give the Illumination Parameters:
    • Azimuth in degrees - corresponds to the illumination source position, from South (y axis), going from 0° to 360°, counter-clockwise.
    • Elevation in degrees - corresponds to the angle between the light source and the surface plan, it goes from 0° to 90°.
    • Height Exaggeration the relief - it is the increment value in the surface vertical scale related to the horizontal scale.
  • click on Apply to create the image

NOTE: After generating the image (Gray level or Shaded) in an IL of the image model, it will be available in the "Control Panel". To visualize the image, just activate the IL which has the image and select the M (monochromatic) representation to draw.

The figures below show the results for two types of images generated from an altimetric grid.

mnt_imaNC.gif - 26652 Bytes mnt_imaSOM.gif - 28206 Bytes
 

See also:
How to generate a Rectangular grid
How to generate a Triangular grid
 

Other DTM products in the SPRING