Thursday, 9 November 2017

qgis - How to use label classes, expressions, and annotations?



I've always found that when it comes to python, vector analysis, QGIS gives ArcGIS a run for its money, hell some of the qgis plugins exceed ArcGIS's performance by a few hours; however, I always have found that compared to ArcGIS, QGIS's labeling system lacks the expressions, sql, and detailed representation. I've tried mapnik, and it's nice, but still it seems to pretty up the problem rather than fix it.



  • How can I improve my own maps done on QGIS, especially with label classes, expressions, and annotations?

  • What needs to be done to enhance QGIS's labeling system in terms of someone writing a plugin or something similar?



Answer



While there is no comfortable editor for label properties available yet, you can achieve the effect of label classes using "data defined labeling":


alt text


This requires some data preparation, but the results should be just what you are looking for.


Also of interest to you might be the new labeling tools by Sourcepole:




  • move label tool … move text labels to a new position

  • rotate label tool … allows for interactive rotation of labels

  • label property tool … opens a dialog where users can manipulate the properties and text of a label


alt text


It's also possible to create multi-line labels:


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QGIS also offers annotation tools:


alt text



A great improvement would be to implement all the options currently available in "rule based" renderer for the labeling engine.


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