Book Image

QGIS 2 Cookbook

By : Mandel, Olaya Ferrero, Anita Graser
Book Image

QGIS 2 Cookbook

By: Mandel, Olaya Ferrero, Anita Graser

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 (14 chapters)
13
Index

Analyzing hydrology


A common analysis from a DEM is to compute hydrological elements, such as the channel network or the set of watersheds. This recipe shows you the steps to do these analysis.

Getting ready

Open the DEM that we prepared in the Preparing elevation data recipe.

How to do it…

  1. In the Processing Toolbox option, find the Fill Sinks algorithm and double-click on it to open it:

  2. Select the DEM in the DEM field and run the algorithm. This will generate a new filtered DEM layer. From now on, we will just use this DEM in the recipe and not the original one.

  3. Open Catchment Area and select the filtered DEM in the Elevation field:

  4. Run the algorithm. This will generate a catchment area layer:

  5. Open the Channel network algorithm and fill it in, as shown in the following screenshot:

  6. Run the algorithm. This will extract the channel network from the DEM, based on the catchment area, and it will then generate it as both a raster and vector layer:

  7. Open the Watershed basins algorithm and fill it in, as...