Generating Shadowed Image

Analyze a triangle or rectangle grid does not give an overall idea, i.e., parameters being modeled, so it is convenient to transform the grid in a more suitable product to be analyzed

A shadowed image generated from a terrain numeric model in TerraAmazon will make possible to view terrain differences in each region. It is generated from the rectangle grid on which is applied a light model. This light model determines the reflected light intensity in a surface point considering a certain light source The model depends on the light source that can be day light or other light source, and the surface reflexion.

The output image resolution (in meters) will have the same rectangle grid that generated it. To generate an image with a different XY resolution, it is necessary to generate another grid with the wanted resolution, and then generate the gray level image. This happens because each grid cell will correspond exactly to a pixel in output image where minimum quota values will be represented by dark pixels and the maximum values by clear pixels.

Select PROCESSING → DTM PROCESSING → SHADOW IMAGE GENERATION in the main menu.

Layer Name: Click on the icon and select the layer.

Dummy Value: check in this box to enter the pixel dummy value. This dummy value will be ignored by the operation to crate the isolines.

Image Style: enter lighting parameters.

Azimuth: correspondent to light source position, starting in the South (Y axis), ranging from 0º to 360º, in anti clock-wise.

Elevation: correspondent to the angle between of light source and the surface layer, ranging from 0º to 90º.

Image Size: Select one image model category.

Height Exaggeration: it is the added value in the surface vertical scale in relation to horizontal scale.

Output Parameters:

SRS: Click on this icon to change the reference system.

Repository: Click on the icon to save the result in a shape file.

Layer Name: enter a name for the output layer.

Resolution: enter X and Y values.

Dimension: enter L and C values.

Click on the OK button.

Note: Before saving the new image the user can adjust azimuth, height exaggeration and elevation and check the result clicking on Preview button.