Viewing posts for the category QGIS
Generating an XYZ ASCII file from a QGIS raster
Someone wrote to me asking if it would be possible to generate an XYZ ASCII file from a single band raster layer in QGIS. No doubt there are more efficient ways (this approach is pretty slow but it works), but I thought it would be fun to show how you can iterate over a raster, writing out the value of each cell into a text file (along with the centroid coordinates for that cell).
How to create a QGIS PDF report with a few lines of python
Sometimes you want to automatically generate a report to reflect the latest state of your data. For example you may be capturing spatial data into a PostGIS database and want a snapshot of that every few hours expressed as a pdf report. This example shows you how you can quickly generate a pdf based on a QGIS project (.qgs file) and a QGIS template (.qpt file).
QGIS course at AfQUA
Kartoza has just wrapped up a three-day Introduction to QGIS course that we gave pro bono at The African Quaternary: Environments, Ecology and Humans conference in Cape Town (AfQUA2015). Thank you to Kelly Kirsten from the local organising committee at the University of Cape Town for inviting us. Admire Nyakudya presented to about fifteen conference delegates from around the world. Attendees ran QGIS 2.6.1 on their own notebooks on the operating system of their choice. Some already use QGIS, some were experiencing QGIS for the first time and some some wanted to compare it with ArcGIS. The course content was guided largely by the QGIS training manual but as we usually do, adapted for the requirements, interests and pace of the class.
How to load a QGIS project in python
Today in a project we are working on we wanted to load a QGIS project. It takes surprisingly few lines of code to make a small standalone application that loads a project and then shows it as a map in a window like this:
A quick hack to select all multipart features in QGIS
Today we wanted to find all the multipart features in this layer:
Setting up a Fedora 21 QGIS Workstation
I have been a long time Ubuntu user (I have actually been using it since Ubuntu 4.10 'Warty Warthog') - the first official release. The advent of Ubuntu saw an end to my distro hopping whilst looking for the 'perfect linux distro'.
How to build and debug QGIS with QtCreator
Here is how I build QGIS with QtCreator under ubuntu 14.04
Gary Sherman wins the Sol Katz award
WMS Legend Plugin for Leaflet
This weekend I was updating our map gallery at http://maps.kartoza.com and I wanted to have WMS legends in my maps. The maps are mostly generated using QGIS server which also produces a nice looking graphic for its getLegendGraphic requests. Since Leaflet does not seem have a legend control out of the box, I wrote a small leaflet plugin to do it.
How to quickly transform a bounding box from one CRS to another using QGIS
Today I needed to convert a bounding box for a tilemill project that I want to bring into QGIS as a tile layer (more on that in a future post if I get it to work...). I needed to convert a bounding box from EPSG:4326 ('Geographic') coordinates to EPSG:3857 (Spherical Mercator). Fortunately it is a fairly trivial process if you don't mind writing a few lines of python in the QGIS python console:
box = QgsRectangle(-19.6875,-37.9962,59.0625,37.4400)
source_crs = QgsCoordinateReferenceSystem(4326)
dest_crs = QgsCoordinateReferenceSystem(3857)
transform = QgsCoordinateTransform(source_crs, dest_crs)
new_box = transform.transformBoundingBox(box)
u'-2191602.4749925746582448,-4578889.0142234507948160 : 6574807.4249777207151055,4500615.8633687794208527'
Running QGIS desktop in a docker container
I love using docker - I have been tracking and learning docker since soon after it was announced and believe it is going to be a real game changer. I've been playing around with the different things one can do in a docker container and of course it is only natural that a 'QGIS guy' such as myself would start to think about using docker with QGIS. QGIS server in a docker container seems like a natural fit, but how about QGIS Desktop? Last night Richard Duivenvoorde and I were sitting around drinking tea and we thought we would give it a quick go - in fact it only took about half an hour to get something working....