Terrain Mapping: Hill Shading (4 Factors Control Effect) (Especially for GATE-Geospatial 2022)

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A map with hill shading is drawn as though there is a very bright light shining on the area normally from the north-west. This light creates ‘shadows’ in the deep valleys and on the mountains. These shadows will show up the shape of the mountains, but not their height. Hill shading may be found on some large-scale maps such as the 1: 250000 series.

Picture Shows Hill Shading

Hill shading is also known as a shaded relief or simply shading. That attempts to simulate how the terrain looks with the interaction between sunlight and surface features.

Four Factors Control the Visual Effects of Hill Shading

Simulate how the terrain looks with the interaction between the sunlight and surface features. Four factors control the visual effects of hill shading:

Diagram Shows Four Factors Control the Visula Effects of Hil …

Sun Azimuth

The direction of the incoming light, ranging from 0 to 3600 degree in a clockwise direction

Image Shows Example of Hill Shading with the Sun՚s Azimuth

The Sun՚s Altitude

The angle of the incoming sunlight measured above the horizon between 00 to 900.

The Surface Slope

Ranges from 00 to 900

The Aspect

Ranges from 00 to 3600

Use the following equation to compute the relative radiance for every cell in the elevation grid or for every triangle in a TIN.

Where,

the relative radiance value of a facet (grid cell or a triangle) .

the facet՚s aspect.

the sun՚s azimuth.

the facet՚s slope.

the sun՚s altitude.

ranges in the value from 0 to 1.0

, the If value of 255 would results in white and 0 results in black.

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