Table of Contents for
OpenLayers 3.x Cookbook - Second Edition

Version ebook / Retour

Cover image for bash Cookbook, 2nd Edition OpenLayers 3.x Cookbook - Second Edition by Antonio Santiago Perez Published by Packt Publishing, 2016
  1. Cover
  2. Table of Contents
  3. OpenLayers 3.x Cookbook Second Edition
  4. OpenLayers 3.x Cookbook Second Edition
  5. Credits
  6. About the Authors
  7. About the Reviewer
  8. www.PacktPub.com
  9. Preface
  10. What you need for this book
  11. Who this book is for
  12. Sections
  13. Conventions
  14. Reader feedback
  15. Customer support
  16. 1. Web Mapping Basics
  17. Creating a simple fullscreen map
  18. Playing with the map's options
  19. Managing the map's stack layers
  20. Managing the map's controls
  21. Moving around the map view
  22. Restricting the map's extent
  23. 2. Adding Raster Layers
  24. Using Bing imagery
  25. Using OpenStreetMap imagery
  26. Adding WMS layers
  27. Changing the zoom effect
  28. Changing layer opacity
  29. Buffering the layer data to improve map navigation
  30. Creating an image layer
  31. Setting the tile size in WMS layers
  32. 3. Working with Vector Layers
  33. Adding a GML layer
  34. Adding a KML layer
  35. Creating features programmatically
  36. Exporting features as GeoJSON
  37. Reading and creating features from a WKT
  38. Using point features as markers
  39. Removing or cloning features using overlays
  40. Zooming to the extent of a layer
  41. Adding text labels to geometry points
  42. Adding features from a WFS server
  43. Using the cluster strategy
  44. Reading features directly using AJAX
  45. Creating a heat map
  46. 4. Working with Events
  47. Creating a side-by-side map comparator
  48. Implementing a work-in-progress indicator for map layers
  49. Listening for the vector layer features' events
  50. Listening for mouse or touch events
  51. Using the keyboard to pan or zoom
  52. 5. Adding Controls
  53. Adding and removing controls
  54. Working with geolocation
  55. Placing controls outside the map
  56. Drawing features across multiple vector layers
  57. Modifying features
  58. Measuring distances and areas
  59. Getting feature information from a data source
  60. Getting information from a WMS server
  61. 6. Styling Features
  62. Styling layers
  63. Styling features based on geometry type
  64. Styling based on feature attributes
  65. Styling interaction render intents
  66. Styling clustered features
  67. 7. Beyond the Basics
  68. Working with projections
  69. Creating a custom control
  70. Selecting features by dragging out a selection area
  71. Transitioning between weather forecast imagery
  72. Using the custom OpenLayers library build
  73. Drawing in freehand mode
  74. Modifying layer appearance
  75. Adding features to the vector layer by dragging and dropping them
  76. Making use of map permalinks
  77. Index

Adding a KML layer

The arrival of Google Maps led to an explosion in the world of GIS and web mapping. Google introduced not only an API but also certain file formats.

The Keyhole Markup Language (KML) has become one of the most extensively-used formats, and it has become an OGC standard. For some more details on the KML standard, refer to https://en.wikipedia.org/wiki/Keyhole_Markup_Language. The following screenshot shows how to create vector layers from a KML file:

Adding a KML layer

This recipe (found in ch03/ch03-kml-layer/) will show you how easy it is to add features from a KML file. You can find the necessary files in the KML format attached to the source code of this book and available on the Packt Publishing website.

How to do it…

In order to import features from KML format into the map, follow these instructions:

  1. Create an HTML file that includes the OpenLayers dependencies and insert a div to contain the map:
    <div id="js-map"></div>
  2. Create the JavaScript file and initialize the map with a base layer and then add the vector layer pointing to the KML source, as follows:
    var map = new ol.Map({
  view: new ol.View({
    zoom: 16,
    center: [3465642, 3500474]
  }),
  target: 'js-map',
  layers: [
    new ol.layer.Tile({
      source: new ol.source.OSM(),
      opacity: 0.4
    }),
    new ol.layer.Vector({
      source: new ol.source.Vector({
        url: 'egypt-pyramids.kml',
        format: new ol.format.KML()
      })
    })
  ]
});

How it works…

The instantiation of the vector layer follows the same structure as seen in the previous GML layer recipe. The only noticeable change is the difference in url and format:

new ol.layer.Vector({
  source: new ol.source.Vector({
    url: 'egypt-pyramids.kml',
    format: new ol.format.KML()
  })
})

OpenLayers makes an AJAX request for the KML file from the string passed to the url property. The format (ol.format.KML) corresponds to the KML file request so that OpenLayers knows how to process the response. The ol.format.KML class provides some properties that can be customized on instantiation. One of which is extractStyles. This property informs OpenLayers whether or not to extract feature styling information from the KML file (such as color and line width) and use it to render on the map. This defaults to true.

There's more…

Like GML, the KML format offers tons of options and possibilities at the cost of complexity. Google has some useful documentation to help developers structure their KML files at https://developers.google.com/kml/documentation

In the KML format, placemarks can have a description attached to them, and if you load a KML file in Google Maps, the placemark's description is shown as a balloon (or a popup) when you click on it. With OpenLayers, this kind of behavior requires some manual intervention to achieve similar results.

See also

  • The Adding a GML layer recipe
  • The Creating features programmatically recipe
  • The Removing or cloning features using overlays recipe