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 data inputs to your model


In this first example, you will identify the portion of a forest within 100 meters from streams (riparian trees). To begin a model, you will need to define the inputs. The graphical modeler will accept the following:

  • Boolean

  • Extent

  • File

  • Number

  • Raster layer

  • String

  • Table

  • Table field

  • Vector layer

To add an input, either double-click on the appropriate category from the Inputs tab or drag the input onto the modeler canvas. The Parameter definition dialog will open. Give the parameter a name and fill in any other details, which change depending on the input that is chosen. When an input parameter is defined and added to the model, it is essentially a conceptual parameter. It will not actually be connected to a GIS data layer until you are ready to run the model.

For this example, we will add a vector layer. We will specify the geometry of the vector data and classify it as a required parameter:

Once you click on OK, the input object is added to the modeler...