Quantum GIS 2.0 Dufour Released

This entry is out-of-date.  Please read: http://opensourcegisblog.blogspot.com/2014/07/qgis-24-chugiak-released.html

Quantum GIS or QGIS 2.0 has been released!  Be sure to check it out on the newly redesigned QGIS website: http://www.qgis.org/en/site/.

New Sleek Looking QGIS Website

The user interface has undergone some improvements aesthetically and functionally.  Several of the plugins appear to be working better--including the heat map add-on--for getting your spatial analysis started. The user can even choose the type of kernel function.  Symbolizing layers also has improved and appears to be easier.

A Heat/Density Map of Healthy Food Stores in Philadelphia

 For a full list of the new features, go here: http://www.qgis.org/en/docs/user_manual/preamble/whats_new.html

If you have not used QGIS before, be sure to check out the user's section: http://www.qgis.org/en/site/forusers/index.html

Lastly a new e-book and book in print has been published by a top QGIS blogger.  Be sure to check it out, even if you have some experience using QGIS before! http://www.packtpub.com/learning-qgis-2-0-to-create-maps-and-perform-geoprocessing-tasks/book

Trivia: Previous releases of QGIS have been named after places.  However, this release is named after a famous cartographer: http://en.wikipedia.org/wiki/Guillaume-Henri_Dufour

Open data combined with open source GIS is an extremely powerful and versatile platform!

CrimeStat & GME vs. ArcGIS: Kernel Density

Many spatial analyses begin with using kernel density in GIS.  In ArcGIS, kernel density is part of the Spatial Analyst Extension.  However, several viable alternatives exist.  For today's post, I chose two of the easiest to implement and the ones that I have had the most success with: CrimeStat and Geospatial Modeling Environment (GME), formerly known as Hawth's Tools. Note: For GME you will also have to have R installed and several spatial packages.  They are both free, so enjoy!

When using these different tools, keep in mind that there are different kernel functions. ArcGIS uses a quadratic estimation while CrimeStat and GME have several. Click on the image below to magnify it.   The maps show density analysis of Wifi spots in New York City.

I chose different kernel functions to highlight the intricacies of density analysis.  In addition, ESRI has a video on performing proper density analysis, which you should check out.

Crimestat is a lightweight program that is relatively straightforward.  GME requires more installation steps but uses a point-and-click interface to generate the density map. After installing GME and R, in GME, be sure to search and use r.setpath to link GME to R. In addition, in GME you can copy, paste, and edit code in the same window--an extremely helpful feature!

Notes: I have been rather frustrated with the kernel density implementation in GRASS and Quantum GIS--even after diving into the help pages and discussion boards.