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

Using arrow symbols

Line features convey location, but sometimes you also need to convey a direction along a line. QGIS recently added a symbol that does just that by turning lines into arrows. In this recipe, we'll symbolize some line features showing historical human migration routes around the world. This data requires directional arrows for us to understand it.

Getting ready

We will use two shapefiles in this example. One is a world boundaries (countries) shapefile and the other is a route shapefile. You can download the countries shapefile here:

You can download the routes shapefile here:

Download these ZIP files and unzip the shapefiles into your qgis_data directory.

How to do it...

We will load the countries shapefile as a background reference layer followed by the route shapefile. Before we display the layers on the map, we'll create the arrow...