ERDAS’ ECW licensing does not allow free redistribution. Therefore, QGIS can’t support .ecw out of the box. However, you can download ERDAS’ SDK – which gives access to .ecw rasters – from their website for free.
If you need ECW support in QGIS and are struggling, you might find Micha Silver’s post “QGIS on Windows with ECW” very helpful.
The OSGeo Education and Curriculum Project provides a knowledge base for everyone interested in working with geoscience in general and open source GIS specifically. Everybody is invited to contribute and upload/link their educational material to the database for the benefit of the community.
The database already contains a number of QGIS related materials, e.g. “GIS Basics with Quantum GIS” by Micha Silver.
Starting from scratch can be painful. Luckily there’s a tool out there that can help: PyQGIS Plugin Builder. The form will build a minimal plugin for you. You’ll get a ready QGIS 1.0 plugin that implements an empty dialog with Ok and Close buttons. You can find a step-by-step description on how to create and modify this dummy plugin at linfiniti.com – “A simple QGIS python tutorial”.
From there, I suggest moving to the PyQGIS Cookbook – a great resource for everything related to QGIS with Python – especially the part about “Developing Python Plugins”. Tim also created a PDF version of the Cookbook (original post) if you prefer it in hard copy.
Yesterday, I picked up an interesting link on QGIS IRC: mapbox.com – “Create beautiful custom maps using open source tools in the cloud”.
Mapbox tile "Word Dark"
MapBox provides open source tools and services for creating and using custom maps. They also design tilesets and host them for free. Currently, there are tiles featuring world maps, maps of the U.S., Haiti, Iraq, Pakistan and Afghanistan.
You can integrate MapBox’s tiles into websites using Google Maps or OpenLayers. For example, in OpenLayers creating a new layer for their “World Dark” tiles would look like this:
var layer = new OpenLayers.Layer.MapBox(
"World Dark",
{ 'layername': layername,
'osm': 0,
'type': file_extension,
'serverResolutions': [156543.0339,78271.51695,39135.758475,19567.8792375,9783.93961875,4891.96980938,2445.98490469,1222.99245234,611.496226172,305.748113086,152.874056543,76.4370282715,38.2185141357,19.1092570679,9.55462853394,4.77731426697,2.38865713348,1.19432856674,0.597164283371],
'resolutions': [156543.0339,78271.51695,39135.758475,19567.8792375,9783.93961875,4891.96980938,2445.98490469,1222.99245234,611.496226172,305.748113086,152.874056543,76.4370282715]
}
);
VisualEyes is an online tool developed at the University of Virginia. It allows you to combine images, maps, charts, video and data into interactive dynamic visualizations.
The examples offer multiple map layers, charts and of course a time slider to navigate through time.
VisualEyes example: Jefferson's Travels to England
Check out: www.viseyes.org.
Kudos to radek at gis.stackexchange.com.
The enhancement request Support for “selected features only” in “Select by location” is now implemented.
Thanks Carson!
Three new label editing tools found their way into the QGIS developer version:
These tools allow you to mix fixed label positions and automatic label positioning inside a project. If the x or y attribute value is NULL, the position will be set automatically. When a label position is changed using “move label tool”, the position is written into the attribute fields and the label position for this feature is fixed.
To use these tools on existing layers, add x, y and rotation attribute fields (type double). By default, all values will be NULL and thus the layer will be labeled automatically. Now you’re ready to move and rotate the labels as you like.
For more information check: www.sourcepole.com
The biggest Austrian GIS Conference “Symposium und Fachmesse für Angewandte Geoinformatik” (AGIT) is once more going to take place in Salzburg from July, 6th – 8th 2011. Papers can be submitted from Dec, 1st 2010 until Feb, 1st 2011. There’s an extended deadline until Feb, 21st 2011 for non-paper submissions.
More information: AGIT – Call for Papers 2011
The evolution of QGIS since July 2002:
QGIS Release Timeline
A cartogram is a map where some variable (e.g. population) is substituted for land area or distance. The geometry of the map is distorted to convey the information of this variable.
“Cartogram Creator” is a Python plugin for QGIS available through Carson Farmer’s repository.
Cartogram Creator icon
To use this plugin, you need a polygon layer with the attribute you want to be represented in the cartogram. I’m using a small file of Austrian regions with population data:
base data (Austrian regions and number of inhabitants)
The small island in the north-east is Vienna, the Austrian capital. With more than 1.5 million inhabitants, it is the region with highest population. This fact should be visible in the resulting cartogram.
I chose to run five iterations of the plugin algorithm. The plugin allows saving of each iteration’s result. This is how the shape of the region changes through the iterations:
cartogram iterations (n=5)
We can see Vienna “growing”. The final result looks like this:
cartogram result after five interations
The cartogram shows pretty clearly that the Vienna region is home to a considerable population.
Free and Open Source GIS Ramblings 