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  • Book Overview & Buying Building Mapping Applications with QGIS
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Building Mapping Applications with QGIS

Building Mapping Applications with QGIS

By : Erik Westra
4.6 (9)
Buy this Book
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Building Mapping Applications with QGIS

Building Mapping Applications with QGIS

4.6 (9)
By: Erik Westra
Buy this Book

Overview of this book

If you are an experienced Python developer who wants to create your own geospatial applications with minimum fuss, this is the book for you. While some familiarity with mapping applications would be an advantage, no prior knowledge of geospatial concepts is required. Even if you've never used QGIS before, this book will quickly get you up to speed.
Table of Contents (11 chapters)
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Preface
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Preface
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What this book covers
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What you need for this book
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Who this book is for
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Conventions
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Reader feedback
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Customer support
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1
1. Getting Started with QGIS
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1. Getting Started with QGIS
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About QGIS
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Linking QGIS and Python
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Summary
2
2. The QGIS Python Console
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2. The QGIS Python Console
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Using the console
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Working with geospatial data in the console
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Scripting the QGIS user interface
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Summary
3
3. Learning the QGIS Python API
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3. Learning the QGIS Python API
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About the QGIS Python APIs
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Deciphering the C++ documentation
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Organizing the QGIS Python libraries
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Using the PyQGIS library
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Summary
4
4. Creating QGIS Plugins
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4. Creating QGIS Plugins
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Getting ready
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Understanding the QGIS plugin architecture
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Creating a simple plugin
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The plugin development process
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Writing a useful plugin
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Possibilities and limitations of plugins
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Summary
5
5. Using QGIS in an External Application
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5. Using QGIS in an External Application
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Introducing Lex
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Getting the data
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Designing the application
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Creating the application's framework
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Adding the user interface
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Connecting the actions
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Creating the map canvas
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Labeling the points
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Filtering the landmarks
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Implementing the zoom tool
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Implementing the pan tool
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Implementing the explore mode
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Further improvements and enhancements
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Summary
6
6. Mastering the QGIS Python API
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6. Mastering the QGIS Python API
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Working with symbol layers
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Combining symbol layers
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Implementing symbol layers in Python
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Implementing renderers in Python
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Working with custom map layers
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Creating custom map canvas items
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Using memory-based layers
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Summary
7
7. Selecting and Editing Features in a PyQGIS Application
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7. Selecting and Editing Features in a PyQGIS Application
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Working with selections
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Using the layer editing mode
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Adding Points
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Editing Points
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Deleting Points and other features
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Adding lines and polygons
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Editing lines and polygons
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Summary
8
8. Building a Complete Mapping Application using Python and QGIS
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8. Building a Complete Mapping Application using Python and QGIS
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Introducing ForestTrails
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Designing the ForestTrails application
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Creating the application
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Obtaining the basemap
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Defining the map layers
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Defining the map renderers
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The Pan Tool
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Implementing the track editing mode
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Summary
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9. Completing the ForestTrails Application
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9. Completing the ForestTrails Application
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The Add Track map tool
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Testing the application
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Vertex snapping
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The Edit Track map tool
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The Delete Track map tool
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The Get Info map tool
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The Set Start Point and Set End Point actions
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The Find Shortest Path action
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Adjusting the toolbar actions
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Suggested improvements
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Summary
10
Index
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Index

Working with selections

The vector layer class, QgsVectorLayer, includes support for keeping track of the user's current selection. Doing this is relatively straightforward: there are methods that set and alter the selection, as well as retrieve the selected features. When features are selected, they are visually highlighted on the screen so that the user can see what has been selected.

Tip

If you create your own custom symbol layer, you will need to handle the highlighting of the selected features yourself. We saw how to do this in Chapter 6, Mastering the QGIS Python API, in the section titled Implementing symbol layers in Python.

While there are several ways in which the user can select features, the most straightforward way is to click on them. This can be implemented by using a simple map tool, for example:

class SelectTool(QgsMapToolIdentify):
    def __init__(self, window):
        QgsMapToolIdentify.__init__(self, window.mapCanvas)
        self.window = window
        self.setCursor...
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Building Mapping Applications with QGIS
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