Review: Building Mapping Applications with QGIS

It seems like over the last year the amount of literature published regarding QGIS has really exploded. In the past few months alone there’s been at least three titles I can think of (Building Mapping Applications with QGISMastering QGIS, and the QGIS Python Programming Cookbook). I think this is a great sign of a healthy project. Judging by this there’s certainly a lot of demand for quality guides and documentation for QGIS.

I recently finished reading one of these titles – Building Mapping Applications with QGIS. (Erik Westra, Packt Publishing 2015) In short, I’m a huge fan of this work and think it may be my favourite QGIS book to date! I’ve read Erik’s previous work, Python Geospatial Development, and thought it was an entertaining and really well written book. He’s clearly got an in-depth knowledge about what he’s writing about and this confidence comes through in his writing. So when I first saw this title announced I knew it would be a must-read for me.

In Building Mapping Applications with QGIS, Erik has created a comprehensive guide through all the steps required to create QGIS plugins and standalone Python applications which utilise the QGIS libraries. It’s not a beginner’s guide to Python or to PyQGIS, but that’s what helps it stand out. There’s no introductory chapters on programming with Python or how to use QGIS and instead Erik dives straight into the meat of this topic. I found this approach really refreshing, as I’m often frustrated when the first few chapters of an advanced work just cover the basics. Instead, Building Mapping Applications with QGIS is packed with lessons about, well, actually building mapping applications!

So, why do I like this book so much? Personally, I think it fills a a really crucial void in the existing QGIS literature. There’s a lot of works covering using QGIS, and a few covering PyQGIS development (eg, the PyQGIS Programmer’s Guide, which I reviewed here). But to date, there hasn’t been any literature that covers developing QGIS based applications in such great depth. It’s just icing on the cake that Erik’s writing is also so interesting and easy to read.

Is there any criticisms I have with this book? Well, there’s one small omission which I would have liked to see addressed. While the chapter Learning the QGIS Python API goes into some detail about how QGIS is built using the Qt libraries and a great deal of depth about interpreting the QGIS c++ APIs, I think it could really benefit from some discussion about both the PyQt and Qt APIs themselves. Since a lot of the QGIS classes are either directly derived from Qt classes or heavily utilise them it’s really important that PyQGIS developers are also directed to the PyQt and Qt APIs. For instance, the Qt QColor class is used heavily throughout PyQGIS, but you won’t find any API documentation on QColor in QGIS’ API. Instead, you need to first consult the PyQt API docs and also the detailed Qt c++ docs. It’s often that you may think the PyQGIS API is missing a crucial method, but consulting the Qt docs reveals that the method is instead implemented in the base classes. It’s an important point to note for mastering PyQGIS development. To be fair, I’m yet to read a PyQGIS book which has nailed the interaction between the QGIS, PyQt and Qt APIs.

Honestly, that’s a really minor quibble with an otherwise outstanding work. I’m so glad Erik’s written this work and strongly recommend it to anyone wanting to take their PyQGIS development skills to the next level.

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