Book Image

OpenLayers Cookbook

Book Image

OpenLayers Cookbook

Overview of this book

Data visualization and analysis has become an important task for many companies. Understanding the basic concepts of GIS and knowing how to visualize data on a map is a required ability for many professionals today. OpenLayers is a JavaScript library to load, display, and render maps from multiple sources on web pages."OpenLayers Cookbook" teaches how to work with OpenLayers, one of the most important and complete open source JavaScript libraries.Through an extensive set of recipes, this book shows how to work with the main concepts required to build a GIS web applicationñ maps, raster and vector layers, styling, theming, and so on."OpenLayers Cookbook" includes problem solving and how-to recipes for the most common and important tasks. A wide range of topics are covered.The range of recipes includes: creating basic maps, working with raster and vector layers, understanding events and working with main controls, reading features from different data sources, styling features, and understanding the underlying architecture."OpenLayers Cookbook" describes solutions and optimizations to problems commonly found.
Table of Contents (15 chapters)
OpenLayers Cookbook
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Using the cluster strategy


As we have seen in the chapter's introduction, the behavior of vector layers is determined by the strategies we attach to them.

Imagine a scenario where we want to show all the museums in every city around the world. What will happen when the user navigates within the map and sets a zoom level to see the whole world? We simply see a cloud of points, all at the same place.

The solution to this problem is to cluster the features on each zoom level.

This recipe shows how easy it is to use the cluster strategy on a vector layer, which is responsible for clustering the features to avoid a situation similar to the one we just mentioned.

How to do it...

  1. Create an HTML file and insert the following code in it:

    <!-- Map DOM element -->
    <div id="ch3_cluster" style="width: 100%; height: 100%;"></div>
    
    <!-- The magic comes here -->
    <script type="text/javascript">
        // Create the map using the specified DOM element
        var map = new OpenLayers.Map...