Book Image

QGIS Python Programming Cookbook, Second Edition - Second Edition

By : Joel Lawhead
Book Image

QGIS Python Programming Cookbook, Second Edition - Second Edition

By: Joel Lawhead

Overview of this book

QGIS is a desktop geographic information system that facilitates data viewing, editing, and analysis. Paired with the most efficient scripting language—Python, we can write effective scripts that extend the core functionality of QGIS. Based on version QGIS 2.18, this book will teach you how to write Python code that works with spatial data to automate geoprocessing tasks in QGIS. It will cover topics such as querying and editing vector data and using raster data. You will also learn to create, edit, and optimize a vector layer for faster queries, reproject a vector layer, reduce the number of vertices in a vector layer without losing critical data, and convert a raster to a vector. Following this, you will work through recipes that will help you compose static maps, create heavily customized maps, and add specialized labels and annotations. As well as this, we’ll also share a few tips and tricks based on different aspects of QGIS.
Table of Contents (16 chapters)
QGIS Python Programming Cookbook - Second Edition
About the Author
About the Reviewer
Customer Feedback

Merging shapefiles

Merging shapefiles with matching projections and attribute structures is a very common operation. In QGIS, the best way to merge vector datasets is to use another GIS system included with QGIS, called SAGA. The OSGeo4W QGIS version for Windows includes SAGA. The KyngChaos distribution of QGIS for OSX includes SAGA. Most other versions and platforms will need SAGA manually installed. In PyQGIS, you access SAGA functions through the Processing Toolbox.

Getting ready

In this recipe, we'll merge some building footprint shapefiles from the adjoining areas into a single shapefile. You can download the sample dataset from the following URL:

Extract the zipped shapefiles to a directory named /qgis_data/tiled_footprints.

How to do it...

We will locate all of the .shp files in the data directory and hand them to the saga:mergeshapeslayers to merge them:

  1. Start QGIS.

  2. From the Plugins menu, select Python Console.

  3. We...