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

Collecting field data

For decades, collecting field observation data from the field into a GIS required hours of manual data entry or, at best, loading data after a trip. Smartphones and laptops with cellular connections have revolutionized this process. In this recipe, we'll use a simple but interesting GeoJSON-based framework to enter information and a map location from any Internet-connected device with a web browser to update a map in QGIS. Note that this example will post the location of the device you are using to a publicly visible website. The information is anonymous but it is visible to anyone.

Getting ready

There is no preparation required for this recipe.

How to do it...

We will load a world boundaries layer and the field data layer onto a QGIS map. Go to the field data mobile website and create an entry, and then refresh the QGIS map to see the update. To do this, we need to perform the following steps:

  1. In the QGIS Python console, add the following GeoJSON layers:

            wb = "https...