What is Quantum GIS

What is Quantum GIS (QGIS) – its a brand of Geographical Information System that is Open Source and so free. Its been around since around 2002 and these days is similarly functional to commercial Geographical Information Systems. In order to understand what Quantum GIS is, lets have a quick look at what a Geographical Information System is.

What a Geographical Information System?

A compact definition would say that…

A GIS is a computer application that allows you to capture, store, search, manipulate, relate and manage maps and information about them.

Quntum GIS can do everything in this definition so lets pull the definition apart a bit…

Capturing maps

By this, I mean digitizing. This is the conversion of paper maps into maps that can be used in the GIS. One path is placing a map on a digitizing tablet and tracing all the points, lines and areas with a (mouse like) puck. Another path is to bring a scanned paper map into QGIS and then, similarly to the digitizing tablet method, trace map features with a mouse. Whichever input method you choose, the things you’ve traced will need further editing and then processing using QGIS map editing modules so that the maps are then usable to QGIS.

Storing maps

Self explanatory really. Of course you could imagine that a GIS would have to store maps…but what an incredible difference this functionality has made to the mapping industry. Taken to an extreme, no more storage facilities for maps and maps produced on demand with the latest version of the map!

Searching maps

This is something most of us are familiar with. Google maps has given most of us the functionality to search for an address. In QGIS though, you can search for something in your own maps. For example…houses built in the 1800s, towns where the average income is low, places where the vegetation quality is poor, etc.

Manipulating maps

Zooming and panning is functionality we’re all familiar with

Relating maps

This one makes me dreamy! Relating maps is such an incredibly powerful feature of most GISs. At its simplest this means overlaying two maps on top of each other and having a look. However, GIS has far more sophisticated functionality than front-of-house map viewing. For example, datasets that were previously impossible to relate to each other can be related in a GIS so long as there’s a common spatial “geocode”…imagine how happy tax departments are that a tax payer’s address can be mapped and related to a motor vehicle registration map. Hmmmm, someone on a low income who owns an expensive sportscar?????

Managing maps

Maps can be managed in all sorts of ways in a GIS. They can be stored, they can be re-projected (made compatible with maps from different sources) if necessary, and they can be recombined to create new maps,

Managing information about maps

An example of this would be a map of houses…although a house might be built to last for decades, during its lifetime it’ll probably be occupied by a number of different families. Land ownership information can be updated using the database functionality of GIS. I hope this simple example illustrates that the database that lies behind a GIS map is a really important aspect of GIS.


I suppose this post is as much about what is a GIS as it is “what is Quantum GIS?”. Quantum GIS is a fully functional GIS that is capable of all of the things a fully functional GIS should be able to do. It is capable of this in a desktop environment, and due to its compatibility with sophisticated spatial databases, it is also a very capable GIS in the corporate environment.