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
Credits
About the Author
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface

Adding elevation data to a line vertices using a digital elevation model


If you have a transportation route through some terrain, it is useful to know the elevation profile of that route. This operation can be accomplished using the points that make up the line along the route to query a DEM and to assign elevation values to that point. In this recipe, we'll do exactly that.

Getting ready

You will need an elevation grid and a route. You can download this dataset from https://github.com/GeospatialPython/Learn/raw/master/path.zip.

Unzip the path directory containing a shapefile and the elevation grid. Place the whole path directory in your qgis_data/rasters directory.

How to do it...

We will need two processing algorithms to complete this recipe. We will load the raster and vector layers, convert the line feature to points, and then use these points to query the raster. The resulting point dataset will serve as the elevation profile for the route. To do this, we need to perform the following steps...