GIS Files 6: Expert GIS concepts

6.2: Standards (2)

Metadata

Metadata is a word that frequently crops up when discussing GIS. It can be described as data about data. It can be very useful if files of digital information include additional information describing the contents of the main part of the file. This concept is inherent in many commonly encountered file types. For example, many graphics file formats like .GIF or .JPG contain a header component that does not specify the image itself but describes the palette of colours present in the image. Similarly, many web pages carry metadata contained in meta-tags at the top of the file.

Metadata is very important in GIS because many different datasets exist, and it is essential to know certain things such as who created it and when, the types of feature it contains, the geographical bounding area and the precision, accuracy and scale. Many standard GIS file types have a header or separate metadata file as part of the data format, or supply the metadata as a written report. A good analogy is to liken metadata to the nutritional information displayed on food packaging.

There has been much effort over recent years in the GI community to create metadata reference archives so that the full range of available datasets can be identified and made accessible. By standardising the way in which metadata is stored it is possible to identify resources that contain common types of information. Therefore, if you are interested in forestry you can access a metadata gateway and find references to forestry information stored across the globe.

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