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

Reprojecting a raster

A core requirement for all geospatial analysis is the ability to change the map projection of data in order to allow different layers to be displayed on the same map. Reprojection can be challenging, but QGIS makes it a piece of cake. Starting with this recipe, we will begin using the powerful QGIS Processing Toolbox. The Processing Toolbox wraps over 600 algorithms into a highly consistent API available to Python and also as interactive tools. This toolbox was originally a third-party plugin named SEXTANTE but is now a standard plugin distributed with QGIS.

Getting ready

As with many recipes in this chapter, we will use the SatImage raster available at

Place this raster in your /qgis_data/rasters directory.

How to do it...

In this recipe, we will use the gdalwarp algorithm of the processing module to reproject our image from EPSG 4326 to 3722. To do this, we need to perform the following steps:

  1. Start QGIS...