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

Converting points to lines to polygons and back – SpatiaLite


The goal of this recipe is identical to the previous recipe, but it covers how to perform the process with data in a SpatiaLite database. You will to turn points into lines and lines into polygons.

Not all methods are available; for those that are not available, you can use the previous recipe. It will also work on a database layer; it just doesn't save the results to the database. So, the results will need to be imported to the database after completion.

Getting ready

You need to load a vector layer of points with a numeric ID indicating order, and an identifier of unique lines or polygons that is shared between points of the same geometry. For example, you can use census_wake_2000_points loaded into SpatiaLite with the geometry field called geom.

How to do it…

Using DB Manager Plugin (comes with QGIS and is in the Database menu), the QspatiaLite plugin, or an alternate SpatiaLite SQL application (command line or GUI), the following...