A map gives all the information about a place according to the scale and projection used for mapping. A two dimensional map is capable of representing the third dimension – relief (elevation and slope) by various methods that have been in practice from ancient times. This chapter covers the methods of showing relief, reading landforms from contours, climatic diagrams and the wind rose diagram.
1. Methods of Representing Relief Features
The important methods of representing relief are hachures, contours, form lines, spot heights, bench marks, trigonometrical points, hill shading and layer colouring. Each method has its own merits and demerits in depicting the relief of the land.
| Method | What it shows | How it is shown on the map |
|---|---|---|
| Hachures | Slopes | Small lines – thicker for steeper slopes, thinner for gentle slopes; slopes above 45° depicted completely in black |
| Contours | Places having the same elevation above mean sea level | Imaginary lines drawn in brown colour |
| Form lines | Features that are not actually surveyed | Broken lines (like contours) |
| Spot heights | Actual height above mean sea level of places surveyed | Dots with their values written beside |
| Bench marks | Actual height of a tall structure – tall building, pillar, bridge or other object of permanent nature | Letters BM with the respective height |
| Trigonometrical stations | Points included in the triangulation survey | A triangle with the actual height of the place |
| Hill shading (levels of gray) | Relief, through shadows | Shadows that would be cast by elevated areas if light was shining from a certain direction |
| Layer colouring | Relief in layers | Each layer given a different colour |