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OpenLayers 3.x Cookbook - Second Edition

By : Peter J. Langley, Antonio Santiago

4 (1)

OpenLayers 3.x Cookbook

4 (1)

By: Peter J. Langley, Antonio Santiago

Overview of this book

OpenLayers 3 is one of the most important and complete open source JavaScript mapping libraries today. Throughout this book, you will go through recipes that expose various features of OpenLayers 3, allowing you to gain an insight into building complex GIS web applications. You will get to grips with the basics of creating a map with common functionality and quickly advance to more complicated solutions that address modern challenges. You will explore into maps, raster and vector layers, and styling in depth. This book also includes problem solving and how-to recipes for the most common and important tasks.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Sections

Conventions

Reader feedback

Customer support

Free Chapter

1. Web Mapping Basics

1. Web Mapping Basics

Introduction

Creating a simple fullscreen map

Playing with the map's options

Managing the map's stack layers

Managing the map's controls

Moving around the map view

Restricting the map's extent

2. Adding Raster Layers

2. Adding Raster Layers

Introduction

Using Bing imagery

Using OpenStreetMap imagery

Adding WMS layers

Changing the zoom effect

Changing layer opacity

Buffering the layer data to improve map navigation

Creating an image layer

Setting the tile size in WMS layers

3. Working with Vector Layers

3. Working with Vector Layers

Introduction

Adding a GML layer

Adding a KML layer

Creating features programmatically

Exporting features as GeoJSON

Reading and creating features from a WKT

Using point features as markers

Removing or cloning features using overlays

Zooming to the extent of a layer

Adding text labels to geometry points

Adding features from a WFS server

Using the cluster strategy

Reading features directly using AJAX

Creating a heat map

4. Working with Events

4. Working with Events

Introduction

Creating a side-by-side map comparator

Implementing a work-in-progress indicator for map layers

Listening for the vector layer features' events

Listening for mouse or touch events

Using the keyboard to pan or zoom

5. Adding Controls

5. Adding Controls

Introduction

Adding and removing controls

Working with geolocation

Placing controls outside the map

Drawing features across multiple vector layers

Modifying features

Measuring distances and areas

Getting feature information from a data source

Getting information from a WMS server

6. Styling Features

6. Styling Features

Introduction

Styling layers

Styling features based on geometry type

Styling based on feature attributes

Styling interaction render intents

Styling clustered features

7. Beyond the Basics

7. Beyond the Basics

Introduction

Working with projections

Creating a custom control

Selecting features by dragging out a selection area

Transitioning between weather forecast imagery

Using the custom OpenLayers library build

Drawing in freehand mode

Modifying layer appearance

Adding features to the vector layer by dragging and dropping them

Making use of map permalinks

Index

Index

Changing layer opacity

When you are working with many layers, both raster and vector layers, you will probably find situations where a layer that is on top of another layer obscures the one below it. This is more common when working with raster WMS layers without the transparent property set to true or tiled layers, such as OpenStreetMaps, and Bing Maps.

In this recipe, we'll create a slider that updates the layer opacity of the topmost layer, revealing a layer underneath as the opacity is lowered. The source code can be found in ch02/ch02-layer-opacity/. Here's a screenshot showing the layer opacity at 60%:

Changing layer opacity

How to do it…

We used jQuery UI to create the slider widget. Here are the steps to create this recipe:

Create an HTML file adding the required OpenLayers dependencies, as well as jQuery UI and dependencies. In particular, here's the markup for the map and opacity panels:
```
<div id="js-map" class="map"></div>
<div class="pane&quot...
```

CONTINUE READING

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Programming languages

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