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

Adjusting imprecise building footprints

Digitizing vector data from raster data is a tedious process. A common task in digitizing is to outline buildings in an image to make footprints for urban analysis. While most buildings are rectangular in shape, building footprints often end up with incongruent angles due to analysts quickly clicking points. In this recipe we'll automatically transform some non-rectangular polygons into rectangles using a simple algorithm developed by José Guerrero, which can be found at the following URL:

Getting ready

You need to download the following zipped shapefile into a directory named shapes in your qgis_data directory:

How to do it...

First we'll set up some reusable functions for geometry calculations. Then we'll load our footprints layer and create a memory layer for corrected footprints...