What it does: This is full-fledged GIS software, designed for creating maps that offer sophisticated, detailed data-based analysis of a geographic regions.
The best-known desktop GIS software is probably Esri's ArcView, a robust, well-supported application that costs quite a bit of money. The open-source QGIS is an alternative to ArcView.
As OpenOffice is to Microsoft Office, QGIS is to ArcView. ArcView enthusiasts argue that Esri's offering is a couple of years ahead of open-source alternatives, has a better-developed interface, enjoys commercial support and is better suited for print output. But QGIS users say the open-source alternative is an excellent program that does a great deal of useful GIS work -- and may even be better than ArcView when it comes to generating maps for the Web, thanks to a plug-in dedicated to generating HTML image maps.
What's cool: QGIS has an enormous amount of GIS functionality, including the ability to create maps, overlay various types of data, do spatial analysis, publish to the Web and more. It can also be enhanced with plug-ins that add support for numerous undertakings, including geocoding, managing underlying table data, exporting to MySQL and generating HTML image maps.
Drawbacks: As with any sophisticated GIS application, learning to use this software entails a serious commitment of time and training. Even in hour-long hands-on sessions with first ArcView and then QGIS, I noticed things that were easier to do in the commercial option. For example, ArcView had a one-click "normalize" function to immediately calculate, say, the percentage of people 65 and over versus the total population from a data table with both columns; in QGIS, I needed to pull up a "field calculator" and create a new column with the formula to do that calculation myself.
Runs on: Linux, Unix, Mac OS X, Windows. (This is one case where installation is more complicated on OS X, since it requires manual installation of several dependencies. There's a one-click installer for Windows.)
Skill level: Intermediate to expert.
Note: If you're interested in GIS and want to consider other free software options, download this PDF listing of Open Source/Non-Commercial GIS Products. And if you're looking for a free open-source desktop GIS program that might be fairly easy to use, Jacob Fenton, director of computer-assisted reporting at American University's Investigative Reporting Workshop, recommends taking a look at the System for Automated Geoscientific Analyses (SAGA) site. Finally, if analyzing geographic data in a conventional database sounds interesting, PostGIS "spatially enables" the PostgreSQL relational database, according to the site.
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