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

Converting a shapefile to KML or GeoJSON

In this recipe, we'll convert a layer to KML and GeoJSON. Google KML is an Open GIS Consortium standard and is supported by the underlying OGR library used by QGIS.

Getting ready

For this recipe, download the following zipped shapefile and extract it to a directory named /qgis_data/hancock:

How to do it...

To convert a shapefile to the KML XML format, we'll load the layer and then use the QgsVectorFileWriter object to save it as a KML file:

  1. Start QGIS.

  2. From the Plugins menu, select Python Console.

  3. First, load the layer and validate it:

            vectorLyr= QgsVectorLayer('/qgis_data/hancock/hancock.shp',
                                      'Hancock' , "ogr") 
  4. Make sure that the layer is loaded correctly:

  5. Next, use the file writer to save it as a KML file by specifying the file type as KML: