Complexities of designing terrain maps illustrated with horizontal hachures

Designing maps involves numerous decisions on the part of the cartographer, while designing terrain maps adds unique complexities. Terrain is often conceptualized as varying in a smooth and continuous manner, leading to data being stored with field-based models, often using raster datasets. The focus of many map design books and other literature, however, is on symbolizing object-based models. Vector layers such as contours and hachures can be derived from grids, but are conceptually abstract and require special consideration for three-dimensional display. We propose a classification scheme for terrain maps based on four principal elements of design: layer tinting, shading, texturing and form lines. We also propose a new method for automating horizontal hachures that illustrates how the latter three elements meet at a critical design juncture where location, orientation, derived attributes and the use of visual variables to symbolize the terrain intersect. Horizontal hachures combine multiple design elements into an innovative methodology, and can also be combined with terrain mapping elements on other design levels.