Ordnance Survey – Great Britain's national mapping agency
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1.1: In the beginning . . . there were maps (2)
Map features
The earliest GIS programmes were developed simply to allow map information to be stored in computerised form. This made maps easier to store, reproduce and update. The process of capturing map information in digital form begins with the classification of all features.
Look at any map – the different shapes and symbols are used to illustrate features. There are four main types of symbol used to depict the different feature types. In fact, all map features can be divided into one of four different categories:
- Point (for example, a cross symbol to represent a church).
- Line (for example, a yellow line to represent a road).
- Polygon shape or Area (for example, a blue area to represent a lake).
- Text (for example, the name of a building).
The map is actually a very sophisticated information source. The human eye is able to interpret a rich amount of information from a map simply from the pictorial content. This is enhanced by the use of textual annotations (names of objects are written on a map in such a way that the letters do not get in the way of the geographical features themselves). GIS works by taking all of this information and recording it in electronic form.
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