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

Performing network analysis

Network analysis allows you to find the most efficient route between two points along a defined network of connected lines. These lines might represent streets, pipes in a water system, the Internet, or any number of connected systems. Network analysis abstracts this common problem so that the same techniques and algorithms can be applied across a wide variety of applications. In this recipe, we'll use a generic line network to perform analysis using the Dijkstra algorithm, which is one of the oldest algorithms used to find the shortest path. QGIS has all of this functionality built-in.

Getting ready

First, download the vector dataset from the following link, which includes two shapefiles, and unzip it to a directory named shapes in your qgis_data directory:

How to do it...

We will create a network graph by defining the beginning and end of our network of lines and then use this graph to determine the...