Shaded Relief

The Origins of Shaded Relief Depiction

The use of shading to emphasize the three-dimensional quality of terrain features on maps goes back at least as far as the 15th century. For example, Leonardo da Vinci's “Map of Tuscany and the Chiana Valley” in 1502 (Figure 1) shows shaded hills and their relation to the river valley network and settlements. This was one of the earliest examples of using shaded relief to represent the actual position and form of surface features on a map.

More common in the 18th and 19th centuries was the use of hachures to represent shadow produced by surface features. The printing and reproduction technologies of the time limited the use of shaded relief to such etched lines or points rather than continuous tones. Hachures were used both pictorially to illustrate archetypal hill and mountain features (Figure 2) as well as more precisely to show surface form lines (Figure 3).

As reproduction technologies improved in the 20th century, shaded relief maps increasingly used continuous variations in tone to represent shadow and light on surface features. Probably of greatest influence in [Page 386]the development of shaded relief depiction in the 20th century was the output of Swiss cartographers, in particular the work of Eduard Imhof. Imhof provided detailed guidance on the use of color, shade, and symbolization in the depiction of relief that continues to be used today in topographic mapping.

Figure 1 Detail From “Map of Tuscany and the Chiana Valley”

Source: Leonardo da Vinci, c. 1502.

Figure 2 Detail From “Map of Vancouver, 1798,” University of Washington Libraries

Shows use of hachures to highlight symbolic three-dimensional mountain features.

Figure 3 Detail from “Map Showing the Line of Boundary Between the United States & British Possessions 1868,” University of Washington Libraries

Shows hachures to represent slope lines.

Automated Shaded Relief from Digital Elevation Models

Computer-generated cartography and GIS have been able to in part reproduce the types of relief shading evident in the manual cartography of the 20th century. By processing a DEM or TIN, it is possible to model the amount of light and shadow falling on every point on a surface. To speed up calculation time required to produce automated shaded relief, it is common for GIS to use a local Lambertian lighting model to approximate the amount of light reflected from every point on a landscape. This tends to be calculated in a similar way to that of gradient and aspect.

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