It’s my pleasure to announce that the updated and extended 2nd edition of Learning QGIS is available now.
I also want to take this opportunity to thank everyone who made the 1st edition such a great success!
This second edition has been updated to QGIS 2.6 and it features a completely new 6th chapter on Expanding QGIS with Python. It introduces the QGIS Python Console, shows how to create custom Processing tools, and provides a starting point for developing plugins.
Overall, the book has grown by 40 pages and the price of the print version has dropped by 3€ :-)
Correct turn restriction information is essential for the vehicle routing quality of any street network dataset – open or commercial. One of the challenges of this kind of information is that these restrictions are typically not directly visible on each map.
This post is inspired by a share on G+ which resurfaced in my notifications. In a post on the Mapbox blog, John Firebaugh presents the OSM iD editor which should make editing turn restrictions straight-forward: clicking on the source link turns the associated turn information visible. By clicking on the turn arrows, the user can easily toggle between allowed and forbidden.
But the issue of identifying wrong turn restrictions remains. One approach to solving this issue is to compare restriction information in OSM with the information in a reference data set.
This is possible by comparing routes computed on OSM and the reference data using a method I presented at FOSS4G (video): a turn restriction basically is a forbidden combination of links. If we compute the route from the start link of the forbidden combination to the end link, we can check if the resulting route geometry violates the restriction or uses an appropriate detour:
illustrative slide from my LBS2014 presentation on OSM vehicle routing quality – read more about this method and results for Vienna in our TGIS paper or the open pre-print version
It would be great to have an automated system comparing OSM and open government street network data to detect these differences. The quality of both data sets could benefit enormously by bundling their QA efforts. Unfortunately, the open government street network data sets I’m aware of don’t contain turn information.
The QGIS documentations team has released an updated version of the user guide:
I’d like to encourage everyone to have a look and explore the content, for example the great tips in the Actions menu section:
On my quest to create test data for spatial statistics, I’ve discovered income data for Austria per municipality on a news paper website:
For further analysis, I decided to limit the area to Vienna and Lower Austria. Since the income data included GKZ “Gemeindekennzahl” IDs, it was possible to join them to municipalities extracted from OpenStreetMap using QuickOSM for QGIS. GRASS v.clean was used to clean the vector topology to the point where PySAL was able to compute spatial weights.
Using PySAL, I then computed income clusters: blue regions represent low clusters while red regions represent high clusters …
The results show a statistically significant cluster of low income in the north west, in the area called Waldviertel, as well as a cluster of high income containing many of the municipalities surrounding Vienna, an area often referred to as the “Speckgürtel” (“bacon belt”).
Today, I’ve released TimeManager 1.2 which adds support for additional time formats: DD.MM.YYYY, DD/MM/YYYY, and DD-MM-YYYY (thanks to a pull request by vmora) as well as French translation (thanks to bbouteilles).
TimeManager now automatically detects formats such as DD.MM.YYYY
But there is more: the QGIS team has released a bugfix version 2.6.1 which you can already find in Ubuntu repos and the OSGeo4W installer. Go get it! And please support the bugfix release effort whenever you can.
As promised in my recent post “Experiments with Conway’s Game of Life”, I have been been looking into how to improve my first implementation. The new version which you can now find on Github is fully contained in one Python script which runs in the QGIS console. Additionally, the repository contains a CSV with the grid definition for a Gosper glider gun and the layer style QML.
Rather than creating a new Shapefile for each iteration like in the first implementation, this script uses memory layers to save the game status.
You can see it all in action in the following video:
(video available in HD)
Thanks a lot to Nathan Woodrow for the support in getting the animation running!
Sometimes there are still hick-ups causing steps to be skipped but overall it is running nicely now. Another approach would be to change the layer attributes rather than creating more and more layers but I like to be able to go through all the resulting layers after they have been computed.
A few weeks ago, I had the pleasure to give an interview about open source GIS for the American magazine XYHT. We talked about the open source development model and the motivation behind contributing to open source projects. You can read the full interview in the November issue.
XYHT is available as a classic print magazine as well as for free online and focuses on “positioning and measurement” topics: