Book Image

Learning QGIS - Second Edition

By : Anita Graser
Book Image

Learning QGIS - Second Edition

By: Anita Graser

Overview of this book

<p>QGIS is a user friendly open source geographic information system (GIS) that runs on Linux, Unix, Mac OSX, and Windows. The popularity of open source geographic information systems and QGIS in particular has been growing rapidly over the last few years. More and more companies and institutions are adopting QGIS and even switching to it&nbsp;their main GIS.</p> <p>Learning QGIS Second Edition is a practical, hands-on guide updated for QGIS 2.6 that provides you with clear, step-by-step exercises to help you apply your GIS knowledge. Through a number of clear, practical exercises, this book will introduce you to working with QGIS quickly and painlessly. This book takes you from installing and configuring 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 perform common geoprocessing and spatial analysis tasks and automate them. We will cover how to achieve great cartographic output and print maps. Finally, you will learn to extend using Python and even create your own plugin.</p>

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Learning QGIS - Second Edition
Anita Graser
Dec, 2014 | 150 pages
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Table of Contents (13 chapters)
Learning QGIS Second Edition
Learning QGIS Second Edition
Credits
Credits
About the Author
About the Author
About the Reviewers
About the Reviewers
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
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
Summary
3
Data Creation and Editing
Data Creation and Editing
Creating new vector layers
Working with feature selection tools
Editing vector geometries
Using the measuring tools
Editing attributes
Reprojecting and converting vector and raster data
Joining tabular data
Summary
4
Spatial Analysis
Spatial Analysis
Clipping rasters
Analyzing elevation / terrain data
Raster calculator
Converting between rasters and vectors
Accessing the raster and vector layer statistics
Creating a heatmap from points
Vector geoprocessing using Processing
Automated geoprocessing with the graphical modeler
Leveraging the power of spatial databases
Summary
5
Creating Great Maps
Creating Great Maps
Advanced vector styling
Labeling
Designing print maps
Summary
6
Extending QGIS with Python
Extending QGIS with Python
Getting to know the Python console
Creating custom geoprocessing scripts using Python
Developing your first plugin
Summary
Index
Index

Analyzing elevation / terrain data

To use terrain-analysis tools, we need an elevation raster. If you don't have any at hand, you can simply download a dataset from the NASA Shuttle Radar Topography Mission (SRTM) at http://dwtkns.com/srtm/ or from any of the other SRTM download services.

Note

If you want to exactly replicate the results in the following exercise, get the dataset called srtm_05_01.zip, which covers a small part of Alaska.

Raster terrain analysis can be used to calculate the slope, aspect, hillshade, ruggedness index, and relief from elevation rasters, as shown in the following screenshot. These tools can be accessed by going to Raster | Terrain analysis, which comes with QGIS by default, but we have to enable it in the plugin manager.

The terrain analysis plugin includes the following tools:

  • Slope: This tool calculates the slope angle for each cell in degrees (based on the first-order derivative estimation)

  • Aspect: This tool calculates the exposition (in degrees, counter-clockwise...

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