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

Visualizing the pgRouting results in QGIS


In the previous recipe, Creating a routing network for pgRouting, we imported a network layer, built the topology, and finally tested the routing. Building on these results, this recipe will show you how to visualize the routing results on a map in QGIS.

Getting ready

You should first go through the previous recipe, Creating a routing network for pgRouting, to set up the necessary PostGIS tables. Alternatively, you can use your own network tables, but be aware that you may have to alter some of the SQL statements if your table uses different column names.

How to do it…

To visualize the results in QGIS, we can use the DB Manager SQL window, as shown in the following screenshot. The extended query that we use here joins the routing results back to the original network table to get the route link geometries, which we want to display on the map:

  1. Open DB Manager by navigating to Database | DB Manager.

  2. In Tree to the left of the dialog, select the database that...