engleski

Hybrid hatching-shading method for depicting of relief in modern maps

In modern cartography today it is normal to present aside from thematic layers also the relief. The development of the technology has enabled several forms of relief depicting. The most common method is the contour mapping, and shaded relief. The contours are lines that connect the points of same height. The shaded relief is the method that presents the areas oriented toward the source of the sun in brighter color, and those oriented opposite darker. The advantage of the contour mapping is that the height differences can be perceived easily, and also the correct height detection is possible. Disadvantage is that relief can not be experienced intuitively – one has to make conscious effort to read map. The shaded relief map is just the opposite – one can immediately perceive the shape of the terrain. Problem is that the dark areas cause that other map elements – annotations, lines, symbols – are not readable. Recently these two techniques are often combined, and shades are also faded in order not to interfere with other map elements. Beside this there is another relief depicting method, which was used before 20th century. This method could in some applications be interesting and good alternative for existing methods. It is hatching method first developed by German major J. G. Lehmann (1765-1811). This method is based on hatching – the hatches are drawn according to the slope of the terrain. They are drawn perpendicular to contour lines, and they vary in length and width. The bigger the slope of the terrain, the shorter and thicker the hatches are. This enables good perception of the slope of the terrain. Also, the hatches are perpendicular to contour lines, and that is the direction of the flow of the water. By the force of the abrasion water often creates the canals in the real world, so when one reads the map drawn with this method, it easily perceives the form of the terrain. The disadvantage of this method is that it creates the same relief map, no matter in what direction the light comes – so one cannot easily perceive the orientation of the terrain. In order to overcome this shortcoming, the combined hatchig-shading method was developed. This method works in a following way: hatches are drawn with their midpoint on the contour, and their direction is perpendicular to the contour. The width of hatch-lines doesn’t depend on the slope of the terrain – instead it depends on the orientation of the terrain, as with shadedrelief map. In this way, the combined hatching-shading method encapsulates advantages of above mentioned three relief depicting methods. Since the hatches are drawn in the place of contours, the height of terrain can be accurately determined ; the direction of hatch-lines shows the direction of the water flow lines ; and finally the width of hatch lines gives the impression of shading, and depicts the orientation of the relief.

Cartography; GIS

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