GIS Files 1: Getting to grips with GIS

1.2: Introducing raster and vector (5)

Raster can be intelligent

In general terms, vector data is more valuable to GIS systems because it can store a large amount of information about the features. Raster data can store the colour values that make up the whole image of an area and can be used in GIS as unintelligent backdrop mapping, like the map image on the previous page, or data from other sources like aerial photographs.

However, in some more specialist applications, raster data can be used to do more than just capture a visual image. The idea of storing a matrix of values across an area is particularly suited to recording measurements of a continuous nature.

For example, archaeologists will often scan an archaeological site with sensors or probes to get a grid of magnetic or electrical readings that may reveal patterns suggesting the presence of structures under the soil (see example above). This is just one example of a scientific use of raster data – and, in fact, such images can also be loaded into a GIS for analysis alongside map information.

The next section, GIS = software + data, looks at how people bring data together with computer software to build useful systems.

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