Book Image

QGIS Python Programming Cookbook, Second Edition - Second Edition

By : Joel Lawhead
Book Image

QGIS Python Programming Cookbook, Second Edition - Second Edition

By: Joel Lawhead

Overview of this book

QGIS is a desktop geographic information system that facilitates data viewing, editing, and analysis. Paired with the most efficient scripting language—Python, we can write effective scripts that extend the core functionality of QGIS. Based on version QGIS 2.18, this book will teach you how to write Python code that works with spatial data to automate geoprocessing tasks in QGIS. It will cover topics such as querying and editing vector data and using raster data. You will also learn to create, edit, and optimize a vector layer for faster queries, reproject a vector layer, reduce the number of vertices in a vector layer without losing critical data, and convert a raster to a vector. Following this, you will work through recipes that will help you compose static maps, create heavily customized maps, and add specialized labels and annotations. As well as this, we’ll also share a few tips and tricks based on different aspects of QGIS.
Table of Contents (16 chapters)
QGIS Python Programming Cookbook - Second Edition
About the Author
About the Reviewer
Customer Feedback

Using XYZ tiled map services

A tiled map service allows you to efficiently display large raster data sets from web services. The raster dataset is broken into evenly-sized tiles at varying resolutions to create predictable naming conventions and bandwidth requirements for large datasets. QGIS now supports this standard as a part of the raster layer API. In this recipe, we'll load the Open Street Map tiled map service.

Getting ready

Open the QGIS Python console by selecting the Plugins menu and then clicking on Python Console.

How to do it...

We will quickly create a QGIS raster layer, and then we'll add it to the map:

  1. Load the raster layer, specifying the type and the web service URL in the data source parameter. We'll also assign it the name OSM (OpenStreetMap):

            rasterLyr = QgsRasterLayer("type=xyz&url=http://c.tile
                                        .png", "OSM", "wms") 
  2. Then, the only remaining step...