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

1. Hybrid hatching-shading method for depicting of relief in modern maps Marjan Sikora Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture University of Split

2. modern cartography – not only thematic layers, but also relief most common methods: contour mapping shaded relief Introduction

3. Contour mapping • contours-lines connecting points of the same height • advantages: • height differences are perceived easily • possible correct height direction • disadvantage: • relief is not experienced intuitively

4. areas oriented toward the source of light are brighter, those oriented opposite darker advantage: the shape of the terrain is intuitively perceived disadvantage: height cannot be determined exactly on darker areas (shades) other map elements (lines, symbols, annotations) are not readable Shaded relief

5. recently in topographic as well as thematic maps those two techniques are combined shaded relief is faded in order not to interfere with other map elements Possible solution

6. alternative is hatching method first developed by German major J. G. Lehmann (1765-1811) based on hatching – the hatches are drawn according to the slope of the terrain Alternative

7. hatches 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 Hatching method

8. advantages method enables good perception of the slope of the terrain the hatches are perpendicular to contour lines, and that is the direction of the flow of the water the force of the abrasion of water often creates the canals in the real world, so this method enables that the form of the terrain could be easily perceived Hatching method

9. dissadvantage it creates the same relief map, no matter in what direction the light comes one cannot easily perceive the orientation of the terrain Hatching method

10. in order to overcome the shortcoming of hatching method, the combined hatching-shading method was developed Hybrid hatching-shading method

11. 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 shaded-relief map Hybrid hatching-shading method

12. for all contour lines do following: draw hatch line on the beginning of the contour perpendicular to the contour set the width of the line according to the formula (angleDifference is the difference between the angle of the light and the angle of the hatch line): lineWidth=minWidth+angleDifference*(maxWidth-minWidth) move along the contour in the clockwise direction for the specified distance repeat the steps 1-3 until the end of the contour is reached Algorithm

13. the program was coded in VBA (Visual Basic for Applications) lanaguage for AutoCAD 2006 Algorithm

14. advantages: 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 the width of hatch lines gives the impression of shading, and depicts the orientation of the relief. Advantages

15. the length of the hatches is same no matter what the slope of terrain is in the place of the bigger slope, the overlap of the hatches occur in the place of the flatter terrain the hatch contours are too distant possible solution – draw hatches variable length – from contour to contour the algorithm has a problem with the partial contour lines – ones that are not closed present algorithm cannot always correctly determine the orientation toward the light source possible solution – user interaction Dissadvantages

16. Comparison

17. the hybrid hatching-shading method can be an interesting alternative to present methods it is aesthetically attractive, and analytically correct and informative further development of the algorithm would solve some shortcomings in the algorithm Conclusion