Topographic maps are graphic relief representations of small extent areas in which the Earth can be considered as “flat”. Normally topographic maps are not limited to the mere representation of surface forms. They include, as well, all kinds of natural and artificial elements information: streams, lakes, dams, urban settlements, communication channels, buildings, vegetation types, administrative borders, electric lines…
It can be distinguished in a topographic map:
- Topographic data that represent relief graphically
- Planimetric data that gather the rest of the elements representation
Information contained in a topographic map requires both a simplification and an abstraction of reality. To interpret a topographic map you must know that:
- It has been used a projection system to make them. That is, geometric transformation methods to “project” on a plane the complex geometry of the Earth’s surface.
- Maps are drawn to scale. That is to say that they are made applying a proportionateness ratio between objects real measures and their representation.
- Topographic maps use a system of symbols to represent information. Dots, lines and coloured or patterned surfaces are used to represent, respectively:
- isolated data,
- linear or equipotential outlines (such as contour lines),
- differentiated areas