QGIS (formerly Quantum GIS) is an open-source, freely distributed software package for viewing and working with geospatial imagery and vector data. It has much of the same functionality that ESRI’s ArcGIS software has. Since ESRI stands astride my industry like a colossus, I suppose that part of the reason for my fondness for QGIS has to do with my tendency to root for the underdog, but I’ve used it quite a bit over the last year and I’m delighted with it.
I’ll go out of my way to use free and open source software rather than commercial software. I used to work for a small remote sensing company that ran on a shoestring, and much of what I did had to be done using free software. At the time (in the late 90s) there was no freeware alternative to ESRI’s ArcGIS other than early GRASS GIS, which was difficult to build and use. At the time I needed mostly to view and process SAR imagery, and for that I used PCI; later, after my company bought Atlantis Scientific in Ottawa, I became an user of their Openev software (which is idle now, but still exists for download on Sourceforge).
It was difficult to be an open source GIS user back then. Not any more, since QGIS has not only an intuitive user interface (not easy for GIS software, which has a lot of moving parts), but has also incorporated most of the other free GIS software that has been developed over the years. QGIS also makes it easy to import and use 3rd party content, including Bing and Google image layers and OpenStreetMap. Furthermore, it’s straightforward to build your own plugins for it in Python, or even to use its constituent libraries to build your own application outside QGIS if you wish.
There is another reason for Arc users to get to know QGIS; if you are working with a customer who needs to use GIS software just once, or who want to learn to use GIS themselves but are operating on a limited budget, the need to purchase commercial software can be a showstopper. QGIS is, conversely, an easy and free download and install, with plenty of online tutorials and support.