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HERE Maps API - Converting a map screen pixel to a geo coordinate

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[[Category:Web]][[Category:Browser]][[Category:Nokia Maps]][[Category:Location]][[Category:Web]][[Category:Nokia Maps]][[Category:Code Snippet]]
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[[Category:Nokia Maps]][[Category:Code Snippet]][[Category:JavaScript]]
{{Abstract|This article explains how to convert a map screen's pixel to a geocoordinate. }}
+
{{Abstract|This article explains how to convert a map screen's pixel to a geocoordinate. This is useful when we want to know the geocoordinates of the point user had clicked. }}
  
 
{{ArticleMetaData
 
{{ArticleMetaData
 
|sourcecode= <!-- Link to example source code e.g. [[Media:The Code Example ZIP.zip]] -->
 
|sourcecode= <!-- Link to example source code e.g. [[Media:The Code Example ZIP.zip]] -->
 
|installfile= <!-- Link to installation file (e.g. [[Media:The Installation File.sis]]) -->
 
|installfile= <!-- Link to installation file (e.g. [[Media:The Installation File.sis]]) -->
|devices= <!-- Devices tested against - e.g. ''devices=Nokia 6131 NFC, Nokia C7-00'') -->
+
|devices=Google Chrome, Mozilla Firefox, Internet Explorer, Opera
 
|sdk= <!-- SDK(s) built and tested against (e.g. [http://linktosdkdownload/ Nokia Qt SDK 1.1]) -->
 
|sdk= <!-- SDK(s) built and tested against (e.g. [http://linktosdkdownload/ Nokia Qt SDK 1.1]) -->
 
|platform= Web browser
 
|platform= Web browser
 
|devicecompatability= <!-- Compatible devices e.g.: All* (must have internal GPS) -->
 
|devicecompatability= <!-- Compatible devices e.g.: All* (must have internal GPS) -->
|dependencies=Nokia Maps 2.1.0
+
|dependencies=Nokia Maps 2.2.3
 
|signing=<!-- Signing requirements - empty or one of: Self-Signed, DevCert, Manufacturer -->
 
|signing=<!-- Signing requirements - empty or one of: Self-Signed, DevCert, Manufacturer -->
 
|capabilities= <!-- Capabilities required by the article/code example (e.g. Location, NetworkServices. -->
 
|capabilities= <!-- Capabilities required by the article/code example (e.g. Location, NetworkServices. -->
|keywords= <!-- APIs, classes and methods (e.g. QSystemScreenSaver, QList, CBase -->
+
|keywords= Nokia Maps, JavaScript, Geocoordinates, onclick
 
|id= <!-- Article Id (Knowledge base articles only) -->
 
|id= <!-- Article Id (Knowledge base articles only) -->
 
|language= <!-- Language category code for non-English topics - e.g. Lang-Chinese -->
 
|language= <!-- Language category code for non-English topics - e.g. Lang-Chinese -->
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|author=[[User:Maveric]]
 
|author=[[User:Maveric]]
 
}}
 
}}
 
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{{SeeAlso|
==Introduction==
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*  [http://developer.here.net/javascript_api Nokia Maps API]
 
+
* [http://developer.here.net/apiexplorer/examples/api-for-js/events/map-coordinate-on-click.html Coordinates on click]  }}
In this article we will convert map screen to a geocoordinate. This is useful when we want to know the geocoordinates of the point user had clicked.
+
  
 
==Prerequisites==
 
==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 API - Add Maps To Any Web Page ]]
+
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 API - Add Maps To Any Web Page]]
  
==Important about Maps credentials==
+
==Important note 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 [http://www.developer.nokia.com/Develop/Maps/Quota/ 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 [https://api.developer.nokia.com/ovi-api Nokia Developer API Registration page].
+
Nokia provides several services options within the Maps API offering. The service is free to use, but you must obtain and use authentication and authorization credentials to use the services. Please read the
 +
[http://developer.here.net/terms_conditions Terms and Conditions] and check the [http://developer.here.net/web/guest/plans Pricing Plans 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 free for free following the instructions  [http://developer.here.net/docs/maps_js/topics/credentials.html#acquiring-credentials here]
  
 
==Implementation==
 
==Implementation==
  
To achieve what we are about to do, we will need to use a method called pixelToGeo, definition below:
+
To achieve what we are about to do, we will need to use a method called {{Icode|pixelToGeo()}}, definition below:
  
 
<code javascript>pixelToGeo (coord) : nokia.maps.geo.Coordinate - this will translate a projected pixel coordinate into a GEO Coordinate.</code>
 
<code javascript>pixelToGeo (coord) : nokia.maps.geo.Coordinate - this will translate a projected pixel coordinate into a GEO Coordinate.</code>
  
We also need to use the EventListener and addListener method, which is defined by the Nokia Maps API reference as follows:addListener (type, listener, useCapture)  ObjectRegisters an event listener, depending on the useCapture parameter, on the capture phase of the event flow or itstarget and bubbling phases.
+
We also need to use the {{Icode|EventListener()}} and {{Icode|addListener()}} method, which is defined by the Nokia Maps API reference as follows: {{Icode|addListener (type, listener, useCapture)}} ObjectRegisters an event listener, depending on the {{Icode|useCapture}} parameter, on the capture phase of the event flow or its target and bubbling phases.
  
 
Parameters:
 
Parameters:
Line 52: Line 52:
 
==Example code==
 
==Example code==
  
This example will add a new eventListener on the map and register the "click" event to fire the function "eventListener". We will get the position user had clicked and this will be converted from pixel projection coordinate to a geocoordinate. The result is sent to screen with JavaScript Alert function.
+
This example will add a new eventListener on the map and register the "click" event to fire the function {{Icode|eventListener()}}. We will get the position user had clicked and this will be converted from a pixel projection coordinate to a {{Icode|geo.Coordinate}}. The result is sent to screen with JavaScript {{Icode|Alert()}} method. Remember to add in your own [[How to Obtain Your Own Nokia appID and Token| AppId and Token]].
  
 
<code javascript>
 
<code javascript>
<html>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<head>
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<html xmlns="http://www.w3.org/1999/xhtml">
<title>Pixel to geocoordinate</title>
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    <head>
<script type="text/javascript" src="http://api.maps.nokia.com/2.0.0/jsl.js" charset="utf-8"></script>
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      <title>Pixel to geocoordinate</title>
</head>
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      <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<body>
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      <script type="text/javascript"
<div id="map" style="z-index: -1; left:0px; top:0px; width: 100%; height: 100%; position: absolute;"></div>
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            src="http://api.maps.nokia.com/2.2.3/jsl.js" charset="utf-8">
<script type="text/javascript">
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        </script>
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    </head>
// Set the authentication token, which is needed by the web-services to authenticate your application.
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    <body>
nokia.maps.util.ApplicationContext.set("authenticationToken", "<Token>");
+
 
+
        <div id="mapContainer" style="z-index: -1; left:0px; top:0px; width: 100%; height: 80%; position: absolute;"></div>
var map = new nokia.maps.map.Display(document.getElementById("map"), {'zoomLevel':4, 'center':[53.1, 15.1]});
+
        <script type="text/javascript">
 +
/////////////////////////////////////////////////////////////////////////////////////
 +
// Don't forget to set your API credentials
 +
//
 +
// Replace with your appId and token which you can obtain when you
 +
// register on http://api.developer.nokia.com/
 +
//
 +
nokia.Settings.set( "appId", "YOUR APP ID GOES HERE");
 +
nokia.Settings.set( "authenticationToken", "YOUR AUTHENTICATION TOKEN GOES HERE");
 +
 
 +
//
 +
/////////////////////////////////////////////////////////////////////////////////////
 +
var map = new nokia.maps.map.Display(document.getElementById("mapContainer"), {'zoomLevel':4, 'center':[53.1, 15.1]});
 
   
 
   
 
var clicked_location = "";
 
var clicked_location = "";
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function eventListener(event){
 
function eventListener(event){
alert("in EventListener");
+
    alert("in EventListener");
 
     clicked_location = map.pixelToGeo(event.displayX, event.displayY);
 
     clicked_location = map.pixelToGeo(event.displayX, event.displayY);
 
 
     alert(clicked_location.toString());
 
     alert(clicked_location.toString());
 
     alert("Adding a Marker there");
 
     alert("Adding a Marker there");
Line 87: Line 98:
 
   
 
   
 
function add_Marker_where_clicked(){
 
function add_Marker_where_clicked(){
 
 
     myMarker = new nokia.maps.map.Marker(clicked_location);
 
     myMarker = new nokia.maps.map.Marker(clicked_location);
 
 
     map.objects.add(myMarker);
 
     map.objects.add(myMarker);
 
 
}
 
}
 
</script>
 
</script>
Line 98: Line 106:
 
</code>
 
</code>
  
==For more on Nokia Maps API==
+
==For more on the Nokia Maps API==
  
 
Please check out the Nokia Maps API full documentation and API reference here:
 
Please check out the Nokia Maps API full documentation and API reference here:
* http://api.maps.nokia.com/
+
* [http://developer.here.net/javascript_api Nokia Maps API]
 
+
You may also access the interactive Nokia Maps API playground,
+
* http://api.maps.nokia.com/2.1.0/playground/index.html
+
 
+
==Tested with==
+
  
* Google Chrome 11.0x
+
You may also access the interactive API explorer
* Mozilla Firefox 5.0
+
* [http://developer.here.net/javascript_api_explorer API explorer]

Revision as of 14:19, 4 January 2013

This article explains how to convert a map screen's pixel to a geocoordinate. This is useful when we want to know the geocoordinates of the point user had clicked.

Article Metadata
Tested with
Devices(s): Google Chrome, Mozilla Firefox, Internet Explorer, Opera
Compatibility
Platform(s): Web browser
Dependencies: Nokia Maps 2.2.3
Article
Keywords: Nokia Maps, JavaScript, Geocoordinates, onclick
Created: Maveric (21 Jun 2011)
Updated: avnee.nathani (06 Jan 2012)
Last edited: jasfox (04 Jan 2013)

Contents

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 API - Add Maps To Any Web Page

Important note about maps credentials

Nokia provides several services options within the Maps API offering. The service is free to use, but you must obtain and use authentication and authorization credentials to use the services. Please read the Terms and Conditions and check the Pricing Plans 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 free for free following the instructions here

Implementation

To achieve what we are about to do, we will need to use a method called pixelToGeo(), definition below:

pixelToGeo (coord) : nokia.maps.geo.Coordinate - this will translate a projected pixel coordinate into a GEO Coordinate.

We also need to use the EventListener() and addListener() method, which is defined by the Nokia Maps API reference as follows: addListener (type, listener, useCapture) ObjectRegisters an event listener, depending on the useCapture parameter, on the capture phase of the event flow or its target and bubbling phases.

Parameters: {String} type Specifies the event type associated with the event for which the user is registering. {Function} listener The function to be called if the event occurs.

Example code

This example will add a new eventListener on the map and register the "click" event to fire the function eventListener(). We will get the position user had clicked and this will be converted from a pixel projection coordinate to a geo.Coordinate. The result is sent to screen with JavaScript Alert() method. Remember to add in your own AppId and Token.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Pixel to geocoordinate</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<script type="text/javascript"
src="http://api.maps.nokia.com/2.2.3/jsl.js" charset="utf-8">
</script>
</head>
<body>
 
<div id="mapContainer" style="z-index: -1; left:0px; top:0px; width: 100%; height: 80%; position: absolute;"></div>
<script type="text/javascript">
/////////////////////////////////////////////////////////////////////////////////////
// Don't forget to set your API credentials
//
// Replace with your appId and token which you can obtain when you
// register on http://api.developer.nokia.com/
//
nokia.Settings.set( "appId", "YOUR APP ID GOES HERE");
nokia.Settings.set( "authenticationToken", "YOUR AUTHENTICATION TOKEN GOES HERE");
 
//
/////////////////////////////////////////////////////////////////////////////////////
var map = new nokia.maps.map.Display(document.getElementById("mapContainer"), {'zoomLevel':4, 'center':[53.1, 15.1]});
 
var clicked_location = "";
var myContainer;
 
map.addListener("click", eventListener); // add the listener for mouse click
 
map.set("baseMapType", map.NORMAL);
 
function eventListener(event){
alert("in EventListener");
clicked_location = map.pixelToGeo(event.displayX, event.displayY);
alert(clicked_location.toString());
alert("Adding a Marker there");
add_Marker_where_clicked();
}
 
 
function add_Marker_where_clicked(){
myMarker = new nokia.maps.map.Marker(clicked_location);
map.objects.add(myMarker);
}
</script>
</body>
</html>

For more on the Nokia Maps API

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

You may also access the interactive API explorer

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