Book Image

Learning QGIS - Third Edition

By : Anita Graser
Book Image

Learning QGIS - Third Edition

By: Anita Graser

Overview of this book

QGIS is a user-friendly open source geographic information system (GIS) that runs on Linux, Unix, Mac OS X, and Windows. The popularity of open source geographic information systems and QGIS in particular has been growing rapidly over the last few years. Learning QGIS Third Edition is a practical, hands-on guide updated for QGIS 2.14 that provides you with clear, step-by-step exercises to help you apply your GIS knowledge to QGIS. Through clear, practical exercises, this book will introduce you to working with QGIS quickly and painlessly. This book takes you from installing and configuring QGIS to handling spatial data to creating great maps. You will learn how to load and visualize existing spatial data and create data from scratch. You will get to know important plugins, perform common geoprocessing and spatial analysis tasks and automate them with Processing. We will cover how to achieve great cartographic output and print maps. Finally, you will learn how to extend QGIS using Python and even create your own plugin.

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Learning QGIS - Third Edition
Anita Graser
Mar, 2016 | 210 pages
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Table of Contents (13 chapters)
Learning QGIS Third Edition
Learning QGIS Third Edition
Credits
Credits
About the Author
About the Author
About the Reviewer
About the Reviewer
www.PacktPub.com
www.PacktPub.com
Preface
Preface
Free Chapter
1
Getting Started with QGIS
Getting Started with QGIS
Installing QGIS
Running QGIS for the first time
Introducing the QGIS user interface
Finding help and reporting issues
Summary
2
Viewing Spatial Data
Viewing Spatial Data
Loading vector data from files
Dealing with coordinate reference systems
Loading raster files
Loading data from databases
Loading data from OGC web services
Styling raster layers
Styling vector layers
Loading background maps
Dealing with project files
Summary
3
Data Creation and Editing
Data Creation and Editing
Creating new vector layers
Working with feature selection tools
Editing vector geometries
Using measuring tools
Editing attributes
Reprojecting and converting vector and raster data
Joining tabular data
Using temporary scratch layers
Checking for topological errors and fixing them
Adding data to spatial databases
Summary
4
Spatial Analysis
Spatial Analysis
Analyzing raster data
Combining raster and vector data
Vector and raster analysis with Processing
Leveraging the power of spatial databases
Summary
5
Creating Great Maps
Creating Great Maps
Advanced vector styling
Labeling
Designing print maps
Presenting your maps online
Summary
6
Extending QGIS with Python
Extending QGIS with Python
Adding functionality using actions
Getting to know the Python Console
Creating custom geoprocessing scripts using Python
Developing your first plugin
Summary
Index
Index

Creating custom geoprocessing scripts using Python

In Chapter 4, Spatial Analysis, we used the tools of Processing Toolbox to analyze our data, but we are not limited to these tools. We can expand processing with our own scripts. The advantages of processing scripts over normal Python scripts, such as the ones we saw in the previous section, are as follows:

  • Processing automatically generates a graphical user interface for the script to configure the script parameters

  • Processing scripts can be used in Graphical modeler to create geoprocessing models

As the following screenshot shows, the Scripts section is initially empty, except for some Tools to add and create new scripts:

Writing your first Processing script

We will create our first simple script; which fetches some layer information. To get started, double-click on the Create new script entry in Scripts | Tools. This opens an empty Script editor dialog. The following screenshot shows the Script editor with a short script that prints the input...

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End of Section 4
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