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.
Table of Contents (13 chapters)
Learning QGIS Third Edition
About the Author
About the Reviewer

Analyzing raster data

Raster data, including but not limited to elevation models or remote sensing imagery, is commonly used in many analyses. The following exercises show common raster processing and analysis tasks such as clipping to a certain extent or mask, creating relief and slope rasters from digital elevation models, and using the raster calculator.

Clipping rasters

A common task in raster processing is clipping a raster with a polygon. This task is well covered by the Clipper tool located in Raster | Extraction | Clipper. This tool supports clipping to a specified extent as well as clipping using a polygon mask layer, as follows:

  • Extent can be set manually or by selecting it in the map. To do this, we just click and drag the mouse to open a rectangle in the map area of the main QGIS window.

  • A mask layer can be any polygon layer that is currently loaded in the project or any other polygon layer, which can be specified using Select…, right next to the Mask layer drop-down list.