Wednesday, July 14, 2010

Display slope or aspect maps with Global Mapper

Global Mapper can easily render a digital elevation model as a shaded relief display. The figure below shows a screenshot of a DEM rendered with Global Mapper's default Atlas Shader.

Sometimes, I may want to see the elevatiion model in terms of its slope values or its aspect (slope direction) values. In other grid analysis software, I would have to generate a separate grid file just to see the slope display or the aspect display. Using Global Mapper, I can simply choose the Slope Shader to render the DEM in terms of its slope values as shown below. Notice the legend on the left shows the slope values in degrees and the corresponding colors. The white values indicate flatter terrain while the darker values indicate steeper terrain.


Similarly, to render the DEM in terms of its aspect, I can simply choose the Slope Direction Shader as shown in the figure below. The legend on the left shows the terrain aspect in degrees and the corresponding colors. North facing terrain is shown in green while south facing terrain is in red; blue indicates east facing terrain and west facing terrain is white.

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