GIS Files 3: Adding real-world information

3.4: Geocoding

This is one of the key functions of GIS, but what does the term geocoding actually mean?

In a way, the concept of geocoding is very similar to the idea of linking to external datasets, for which the river data example was used in section 3.2. Geocoding describes another way of importing non-map data into the GIS such that its geographic properties can be identified and the records positioned in space. However, unlike the linking method in which the additional attribute table remains external to the mapped layer, when a table is geocoded it becomes a new map layer in its own right. Coordinate points are assigned to the geocoded table so that it can be used on its own to display the locations of the objects concerned.

OK, we may have lost you, so… Geocoding is easier to explain with a worked example:

It usually takes place with a list of locations with known addresses. Imagine you have a simple table of British football clubs containing the name of the club and the postcode. To geocode this list you have to process each record against the postcode data in the GIS. There are already several GIS data products that store the National Grid coordinates for every postcode in the country. The National Grid coordinates from the postcode product get copied across to join the football club list. This creates a new football club layer that can be added to the GIS.

Geocoding is often applied to address lists. Not many people know the National Grid coordinates of where they live so any list of people's addresses needs to be geocoded to load it into a GIS. Any company – a bank for example – which holds an address list of customers can geocode this information and instantly analyse their geographic distribution. This may reveal trends that the bank would otherwise be unaware of – areas of particularly high or low customer density – which may suggest reasons for the successful recruitment of customers. We will look at how organisations are using GIS to improve their decision making in greater detail in the next chapter.

Finally, in the last section of this chapter (Section 3.5), we look at the way that geospatial data is structured and can affect the amount of information which can be analysed in a GIS.

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