Book Image

QGIS 2 Cookbook

By : Alex Mandel, Víctor Olaya Ferrero, Anita Graser, Alexander Bruy
Book Image

QGIS 2 Cookbook

By: Alex Mandel, Víctor Olaya Ferrero, Anita Graser, Alexander Bruy

Overview of this book

QGIS is a user-friendly, cross-platform desktop geographic information system used to make maps and analyze spatial data. QGIS allows users to understand, question, interpret, and visualize spatial data in many ways that reveal relationships, patterns, and trends in the form of maps. This book is a collection of simple to advanced techniques that are needed in everyday geospatial work, and shows how to accomplish them with QGIS. You will begin by understanding the different types of data management techniques, as well as how data exploration works. You will then learn how to perform classic vector and raster analysis with QGIS, apart from creating time-based visualizations. Finally, you will learn how to create interactive and visually appealing maps with custom cartography. By the end of this book, you will have all the necessary knowledge to handle spatial data management, exploration, and visualization tasks in QGIS.
Table of Contents (19 chapters)
QGIS 2 Cookbook
About the Authors
About the Reviewers

Cropping rasters

Sometimes, the raster data you have for a theme is just much larger than the actual extent of your study area or map. Or, in the case of scanned maps, you have extra nonmap information around the outside edge. In these cases, you want to cut out a portion of your raster.

Getting ready

You'll need a raster file that you want to cut a portion of. In this example, we will use the North Carolina whole state elevation model (elev_state_500m.tif) and cut it with the outline of Wake County (county_wake.shp). Load both of these files in a fresh QGIS project.

How to do it…

The easiest way to do this is to use a polygon mask layer. The vector mask can be a rectangle, but it doesn't have to be. The outline of a single polygon works best, though.


An alternate method would be to determine the bounding box (bbox) coordinates of the extent that you want with the Capture Coordinate tool or to draw the rectangle directly on the map.

  1. Go to Raster | Extraction | Clipper.

  2. Set Input file (raster...