Book Image

QGIS:Becoming a GIS Power User

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

QGIS:Becoming a GIS Power User

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

Overview of this book

The first module Learning QGIS, Third edition covers the installation and configuration of QGIS. You’ll become a master in data creation and editing, and creating great maps. By the end of this module, you’ll be able to extend QGIS with Python, getting in-depth with developing custom tools for the Processing Toolbox. The second module QGIS Blueprints gives you an overview of the application types and the technical aspects along with few examples from the digital humanities. After estimating unknown values using interpolation methods and demonstrating visualization and analytical techniques, the module ends by creating an editable and data-rich map for the discovery of community information. The third module QGIS 2 Cookbook covers data input and output with special instructions for trickier formats. Later, we dive into exploring data, data management, and preprocessing steps to cut your data to just the important areas. At the end of this module, you will dive into the methods for analyzing routes and networks, and learn how to take QGIS beyond the out-of-the-box features with plug-ins, customization, and add-on tools. This Learning Path combines some of the best that Packt has to offer in one complete, curated package. It includes content from the following Packt products: ? Learning QGIS, Third Edition by Anita Graser ? QGIS Blueprints by Ben Mearns ? QGIS 2 Cookbook by Alex Mandel, Víctor Olaya Ferrero, Anita Graser, Alexander Bruy
Table of Contents (6 chapters)

Chapter 8. Raster Analysis II

In this chapter, we will cover the following recipes:

  • Calculating NDVI
  • Handling null values
  • Setting extents with masks
  • Sampling a raster layer
  • Visualizing multispectral layers
  • Modifying and reclassifying values in raster layers
  • Performing supervised classification of raster layers

Introduction

Following the previous chapter, this chapter introduces some additional techniques for raster analysis. This chapter will show you how to work with images, how to modify raster values and classify them, and how raster layers can be used along with vector layers, thus extending the set of tools that were introduced in the recipes in the previous chapter.

Calculating NDVI

The Normalized Differential Vegetation Index is a very popular vegetation index that gives us useful information about the presence or absence of live green vegetation.

Getting ready

NDVI is calculated using a band with red spectral reflectance values, and another one with near-infrared reflectance values...