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  • Book Overview & Buying QGIS 2 Cookbook
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QGIS 2 Cookbook

QGIS 2 Cookbook

By : Mandel, Olaya Ferrero, Anita Graser
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QGIS 2 Cookbook

QGIS 2 Cookbook

5 (1)
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)
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13
Index

Handling null values


Null values are a particular type of values that are used to indicate cells where the value for a given layer is not defined. Understanding how to use them is important to avoid wrong results when performing analyses but also to use them as a tool to get better and more correct results. This recipe explains some of the fundamental ideas about null values in raster layers.

How to do it…

The watershed.tif layer contains the area of a watershed. Cells inside the watershed are cells from which water will eventually flow into the outlet point of the watershed. The remaining cells belong to a different watershed. To mask the DEM with the watershed mask, follow these steps:

  1. Open the watershed.tif layer.

  2. Open the identify tool and check whether the cells that belong to the watershed have a value of 1, and the ones outside, have a value of no data.

  3. Try clicking inside and outside the watershed; in your Identify Results dialog, you will see the results, as shown in the following screenshot...

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QGIS 2 Cookbook
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