Monthly Archives: February 2012

Extract X and Y coordinates from a spatial table in Spatialite

A quick note on adding two columns with X and Y values in a vector layer in spatialite. Spatialite stores the information about the geometry in binary format in the ‘Geometry’ field.

You can use the Spatialite function AsText() to convert and extract these values as a Well Known Text (WKT), which is an easy to read format. If you for example have a spatial table ‘Waypoints’ with two columns ‘PKUID’ and ‘Geometry’, you can extract a column with WKT values using: Continue reading

Quick multi attribute edit in QGIS

There seem to be a lot of momentum in the development of QGIS and QGIS plug-ins. Existing plug-ins are regularly updated while new plug-ins are released frequently. One recently released plugin is the quick multi attribute edit plugin. It offers one simple, albeit very handy feature; one click editing of multiple features in a vector layer. Continue reading

Split strings in SQLite

I am just back from vegetation survey in Kenya and Uganda. Before starting with the analysis, I will have to go through the more boring data entry and organization. I will use a Spatialite database to store all the data as it plays nicely together with QGIS as well as R. For example, importing the waypoint data (gpx format) into a spatialite database is a breeze with the QSpatialite plugin for QGIS.

One problem is that data and time in the gpx file are given in one field, in the form ‘2011/11/01 5:49:41+00‘. There are various ways I could split this before importing in the SQLite database, e.g., using R or a spreadsheet. But how to do this after importing the data in the Spatialite database? The date + time are imported in the field ‘time‘. Continue reading

Nederlandse (Dutch) QGIS community

I just came across the Dutch QGIS site: www.qgis.nl. The objective of the website is “to create a platform for native speakers AND to discuss / explore typical dutch ideas or problems”.

But the tutorials on this site will not only be useful for the Dutch (speaking) community. All tutorials (that I have seen) are available in both Dutch and English. Check it out…

New “Control Rendering Order” Option in QGIS

I just installed the latest QGIS development version (build 1.9.90-Alpha), and one of the changes I noticed was the option “Control rendering order” in the layers pane. I had to Google to check out what this new option was about. As Darren Cope explains in his blog, it allows you to decouple the way layers are organized in the legend (“Layers” pane) from the order they are rendered (drawn) on the canvas (controlled via the “Layer order” pane.). Continue reading