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Adding elevation to a line from a DEM in PostGIS and maintaining accurate measures

Posted by: Gavin Fleming | in PostGIS, QGIS | 3 months, 3 weeks ago | Comments

This is the second in a three part series on the behind-the-scenes GIS work that can go into planning a complex event, in this case the Cape Town Marathon.

How to create a point distance marker layer along a line in PostGIS

Posted by: Gavin Fleming | in GRASS GIS, PostGIS, QGIS | 4 months ago | Comments

This is part 1 of a 3-part series.

QGIS, InaSAFE, OpenStreetMap, and GeoNode in Understanding Risk 2018

Posted by: Ismail Sunni | in Conference, GeoNode, InaSAFE, QGIS | 6 months ago | Comments

Some QGIS 3 Browser Improvements - Small Things Matter

Posted by: Admire Nyakudya | in QGIS | 9 months, 2 weeks ago | Comments

Well, QGIS 3 has been out for a couple of weeks now with lots of new functionality. While you are still feeling your way around all the new features I thought I could highlight some of the improvements to the browser panel that will make you fall further in love with QGIS. 

A new plugin to manage land (survey) parcels in QGIS

Posted by: Admire Nyakudya | in QGIS | 10 months, 2 weeks ago | Comments

Kartoza releases the CoGo Plugin for QGIS

Kartoza recently published the CoGo Plugin (aka Parcel Plugin) in the QGIS plugin repository. This plugin expands the group of plugins designed to manage SDI (Spatial Data Infrastructure). CoGo ('coordinate geometry') refers to its ability to handle both types of coordinates used in land surveying, namely cartesian coordinates (x,y; long/lat) and polar coordinates (bearing and distance).

Changing the line direction of line features using the geometry generator in QGIS

Posted by: Admire Nyakudya | in QGIS | 1 year, 1 month ago | Comments

I have been playing around with roads layers and wanted to change the line directions for some of my features. I looked around for solutions to do this in QGIS and saw that I could use the swap vector direction plugin in QGIS or ST_reverse in PostgreSQL. But I wanted to find a non destructive way to do this as I did not want to alter my data. I decided to try the geometry generator in QGIS.

How to resolve issues with QGIS 3 Processing Dialog Layouts on MacOS

Posted by: Tim Sutton | in QGIS | 1 year, 2 months ago | Comments

If you are using QGIS 3 master builds on MacOS and encounter issues with the display of processing dialog layouts like this:

Create a custom reference grid in QGIS composer

Posted by: Gavin Fleming | in QGIS | 1 year, 2 months ago | Comments

If you need to create a reference grid like this for your map, here's a simple method.

Report back on the first QGIS User Conference in Nødebo, Denmark

Posted by: Gavin Fleming | in Education, QGIS | 3 years, 6 months ago | Comments

I finally have some time to sit down and write up some thoughts on the QGIS User Conference and Developer Meeting (aka Hackfest) that we just held in Nødebo, Denmark. First up I need to thank Lene Fischer, who was the organiser and wowed us all with her relaxed and competent organisational approach to the conference. Thanks also to the University of Copenhagen School of Forestry - they sponsored the event by providing the venue and accommodation - and the venue was absolutely awesome with little cottages in the forest and all sorts of interesting diversions scattered around the forest. Lene gave me a list of names of people who helped to organise the event - I am sorry I have only got your first names but a very big thank you to you all!

How to run a Linux GUI application on OSX using Docker

Posted by: Gavin Fleming | in Docker, QGIS | 3 years, 7 months ago | Comments

Ok so here is the scenario:

Generating an XYZ ASCII file from a QGIS raster

Posted by: Gavin Fleming | in FOSSGIS, QGIS | 3 years, 9 months ago | Comments

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

Posted by: Gavin Fleming | in FOSSGIS, QGIS | 3 years, 9 months ago | Comments

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

Posted by: Gavin Fleming | in Education, QGIS | 3 years, 10 months ago | Comments

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

Posted by: Gavin Fleming | in QGIS | 3 years, 10 months ago | Comments

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

Posted by: Gavin Fleming | in FOSSGIS, QGIS | 3 years, 11 months ago | Comments

Today we wanted to find all the multipart features in this layer:

Setting up a Fedora 21 QGIS Workstation

Posted by: Gavin Fleming | in FOSSGIS, QGIS, Uncategorised | 3 years, 11 months ago | Comments

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

Posted by: Gavin Fleming | in QGIS | 4 years ago | Comments

Here is how I build QGIS with QtCreator under ubuntu 14.04

Gary Sherman wins the Sol Katz award

Posted by: Gavin Fleming | in QGIS | 4 years, 3 months ago | Comments

This year Gary Sherman won the annual Sol Katz award. To quote the OSGEO page about the award:

WMS Legend Plugin for Leaflet

Posted by: Gavin Fleming | in Leaflet, QGIS | 4 years, 3 months ago | Comments

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

Posted by: Gavin Fleming | in FOSSGIS, QGIS | 4 years, 4 months ago | Comments

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)
new_box.toString()
u'-2191602.4749925746582448,-4578889.0142234507948160 : 6574807.4249777207151055,4500615.8633687794208527'

 

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