Book Image

Mastering QGIS - Second Edition

By : Kurt Menke, GISP, Paolo Corti, Richard Smith Jr., GISP, Luigi Pirelli, John Van Hoesen, GISP
Book Image

Mastering QGIS - Second Edition

By: Kurt Menke, GISP, Paolo Corti, Richard Smith Jr., GISP, Luigi Pirelli, John Van Hoesen, GISP

Overview of this book

QGIS is an open source solution to GIS. It is widely used by GIS professionals all over the world. It is the leading alternative to the proprietary GIS software. Although QGIS is described as intuitive, it is also by default complex. Knowing which tools to use and how to apply them is essential to producing valuable deliverables on time. Starting with a refresher on the QGIS basics, this book will take you all the way through to creating your first custom QGIS plugin. From the refresher, we will recap how to create, populate, and manage a spatial database. You’ll also walk through styling GIS data, from creating custom symbols and color ramps to using blending modes. In the next section, you will discover how to prepare vector, heat maps, and create live layer effects, labeling, and raster data for processing. You’ll also discover advanced data creation and editing techniques. The last third of the book covers the more technical aspects of QGIS such as using LAStools and GRASS GIS’s integration with the Processing Toolbox, how to automate workflows with batch processing, and how to create graphical models. Finally, you will see how to create and run Python data processing scripts and write your own QGIS plugin with pyqgis. By the end of the book, you will understand how to work with all the aspects of QGIS, and will be ready to use it for any type of GIS work.
Table of Contents (19 chapters)
Mastering QGIS - Second Edition
Credits
Foreword
About the Authors
About the Reviewer
www.PacktPub.com
Preface
Index

Georeferencing imagery


Maps and aerial photographs in hard copy have a lot of valuable data on them. When this data needs to be brought into a GIS, they are digitally scanned to produce raster imagery. The output of a digital scanner has a coordinate system, but it is a local coordinate system created by the scanning process. The scanned imagery needs to be georeferenced to a real-world coordinate system before it can be used in a GIS.

Georeferencing is the process of transforming the coordinate reference system (CRS) of a raster dataset into a new coordinate reference system. Often, the process transforms the CRS of a spatial dataset from a local coordinate system to a real-world coordinate system. Regardless of the coordinate systems involved, we'll call the coordinate system of the raster to be georeferenced the source CRS and the coordinate system of the output the destination CRS. The transformation may involve shifting, rotating, skewing, or scaling the input raster from source coordinates...