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

Reading features directly using Protocols


OpenLayers allows us to read data from different origins and sources. As we have described in the chapter's introduction, OpenLayers offers the helper classes: protocols and formats.

Protocols are designed to simplify the task of retrieving data from different origins: via HTTP, from an WFS server, and so on.

On the other hand, formats simplifies the task of reading from (or writing to) a given data format. It is very common to load data from different origins and know how to work directly with protocols that can incredibly simplify this task.

As an example, this recipe shows how we can add features from different data sources in the same vector layer, by working directly with the protocol instances.

How to do it...

  1. Create an HTML file and add the OpenLayers dependencies. Then create a DOM element to hold the map:

    <!-- Map DOM element -->
    <div id="ch3_protocol" style="width: 100%; height: 100%;"></div>
  2. Next, initialize the map, add some...