Book Image

Mastering QGIS - Second Edition

By : Kurt Menke, GISP, Paolo Corti, Richard Smith Jr., GISP, Luigi Pirelli, John Van Hoesen, GISP
Book Image

Mastering QGIS - Second Edition

By: Kurt Menke, GISP, Paolo Corti, Richard Smith Jr., GISP, Luigi Pirelli, John Van Hoesen, GISP

Overview of this book

QGIS is an open source solution to GIS. It is widely used by GIS professionals all over the world. It is the leading alternative to the proprietary GIS software. Although QGIS is described as intuitive, it is also by default complex. Knowing which tools to use and how to apply them is essential to producing valuable deliverables on time. Starting with a refresher on the QGIS basics, this book will take you all the way through to creating your first custom QGIS plugin. From the refresher, we will recap how to create, populate, and manage a spatial database. You’ll also walk through styling GIS data, from creating custom symbols and color ramps to using blending modes. In the next section, you will discover how to prepare vector, heat maps, and create live layer effects, labeling, and raster data for processing. You’ll also discover advanced data creation and editing techniques. The last third of the book covers the more technical aspects of QGIS such as using LAStools and GRASS GIS’s integration with the Processing Toolbox, how to automate workflows with batch processing, and how to create graphical models. Finally, you will see how to create and run Python data processing scripts and write your own QGIS plugin with pyqgis. By the end of the book, you will understand how to work with all the aspects of QGIS, and will be ready to use it for any type of GIS work.
Table of Contents (19 chapters)
Mastering QGIS - Second Edition
Credits
Foreword
About the Authors
About the Reviewer
www.PacktPub.com
Preface
Index

Chapter 11. PyQGIS Scripting

This chapter is focused on a specific use case or user. QGIS can be used in many different ways, and the GIS user is an eclectic user who has many different ways to interact with data and QGIS tools. The main focus of this chapter is a user who has an algorithm and wants to integrate it with QGIS.

An algorithm can be an external program, such as a water-modeling tool, or a Processing Toolbox's set of instructions.

It's possible to interact with QGIS in many different ways, from experimenting with PyQGIS in the Python console, to creating plugins that control events generated by QGIS. This chapter will give you an overview of the following topics:

  • Learning Python

  • Loading rasters by code

  • Loading vectors by code from files or database

  • Describing vector structure and how to browse and edit features

  • Using Processing Toolbox algorithms by code and executing your custom algorithm

  • Calling external algorithms

  • Interacting with canvas events to draw or pick values from a raster...