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Revision as of 02:41, 2 January 2012 by hamishwillee (Talk | contribs)

HERE Maps API - Zooming to all Markers

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This article shows how to show a map and zoom to several markers, with Nokia Maps.

Article Metadata
Compatibility
Platform(s): Web browser
Dependencies: Nokia Maps 2.1.0
Article
Created: Maveric (21 Jun 2011)
Updated: avnee.nathani (31 Dec 2011)
Last edited: hamishwillee (02 Jan 2012)

Contents

Introduction

An important use case would be when you have more than one Marker on the map and in a container, then would like to display all of the Markers for that container visible on the screen at the same time. To achieve this, you would need to know what is the correct zoom level so that all of the Markers become visible.

Prerequisites

Nokia Maps API supported web browser (basically any modern web browser)

The example assumes you have already added the Nokia Maps to your web page as explained in the previous article "Nokia Maps - add the map to any web page"

Important about Maps credentials

Nokia provides several services options within the Maps API offering. The service is free to use, but if you complete the free registration process and obtain authentication and authorization credentials, your application will have priority access to the service and will thus avoid a potential performance penalty. Please read the Location API Business Models and Usage Restrictions page to decide which business model best fits your needs. Authentication requires unique Maps API credentials, namely an AppId and a token. You can get these credentials from the Nokia Developer API Registration page.

Implementation

We will need the concept of BoundingBox when we define the area that will later cover the map markers. Here is the definition of it:

What is a Bounding box?

A bounding box defines a rectangular area in a geographic coordinate system. As the bounding box is specified by its top-left and bottom-right corner the box is not necessarily the smallest rectangle spanned by these two points; it is possible to define bounding boxes that are wider than 180° or higher than 90° (i.e., by setting the longitude of top-left corner to a bigger value than the longitude of the bottom-right corner). Bounding box class is immutable.

Creating the map Markers

Let's first create three map Markers. Each marker will have a geocoordinate of it's own and they are type of Standard markers by default.

myMarkerOne  = new nokia.maps.map.Marker([22.1,10.1]);
myMarkerTwo = new nokia.maps.map.Marker([53.1,63.1]);
myMarkerThree = new nokia.maps.map.Marker([22.1,13.1]);

Creating the map Container and add the Markers into it

To carry the map Markers, we will also need to define a new Container. We will use the "add" method to put each of the marker object inside the Container:

var myContainer = new nokia.maps.map.Container()
 
myContainer.objects.add(myMarkerOne);
myContainer.objects.add(myMarkerTwo);
myContainer.objects.add(myMarkerThree);
 
map.objects.add(myContainer)

Zooming to the Bounding box covering all Markers in the Container:

Finally we will set the map ZoomLevel to cover all the Marker coordinates. This is achieved by calling the "zoomTo" method on the map, to which we will give as parameter the object that will be received by calling "getBoundingBox" method on the "myContainer".

    map.zoomTo(myContainer.getBoundingBox(),false,true);

After this definition the BoundingBox is available for zoomTo function, which will zoom the map to the given bounding box. If the keepCenter flag (default is false) is used, the size of the viewport will be increased such that the original center is still located in the center of the viewport.

Note: This operation may use a platform specific animation if this is indicated by the corresponding optional animation string.

Example code

<html>
<head>
<title>Marker on the Map</title>
<script type="text/javascript"
src="http://api.maps.nokia.com/2.0.0/jsl.js" charset="utf-8">
</script>
</head>
<body>
<div id="map" style="z-index: -1; left:0px; top:0px; width: 100%; height: 100%; position: absolute;"></div>
<script type="text/javascript">
 
// Set the authentication token, which is needed by the web-services to authenticate your application.
nokia.maps.util.ApplicationContext.set("authenticationToken", "<Token>");
 
var map = new nokia.maps.map.Display(document.getElementById("map"), {'zoomLevel':0, 'center':[53.1, 15.1]});
 
map.set("baseMapType", map.NORMAL);
 
myMarkerOne = new nokia.maps.map.Marker([19.119, 72.8957]);
myMarkerTwo = new nokia.maps.map.Marker([19.119, 73.8957]);
myMarkerThree = new nokia.maps.map.Marker([19.119, 74.8957]);
 
var myContainer = new nokia.maps.map.Container()
 
myContainer.objects.add(myMarkerOne);
myContainer.objects.add(myMarkerTwo);
myContainer.objects.add(myMarkerThree);
 
map.objects.add(myContainer)
 
map.zoomTo(myContainer.getBoundingBox(),false,true);
 
</script>
</body>
</html>

Screenshot

NokiaMapsZoomtoMultipleMarkers.png

For more on Nokia Maps API

Please check out the Nokia Maps API full documentation and API reference here:

You may also access the interactive Nokia Maps API playground,

Tested on

  • Google Chrome 11.0x
  • Mozilla Firefox 5.0´
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