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

Adding algorithms to your model


Algorithms are added to the graphical modeler in the same way as inputs. Find the algorithm from the Algorithms tab, and either double-click on it or drag it onto the modeler canvas. You can search for tools as you would in the Processing Toolbox. Type the name into the search box at the top of the Algorithms tab:

Here we see the Algorithms tab with buffer being used as the search term.

In the Algorithms tab, there is a special category named Modeler-only tools. The three tools—Calculator, Raster layer bounds, and Vector layer bounds—do not appear in the Processing Toolbox. They are tools that only make sense when they are used in the context of the graphical modeler:

The Calculator tool is perhaps the most commonly used of the three tools. It allows you to perform arithmetic calculations on numeric outputs from other algorithms. For example, if you use one of the statistical output tools such as Raster layer statistics in your model or if you have numeric inputs...