Friday, 22 September 2017

Displaying altitude with Google Maps





We will look at displaying additional positional information with Google Maps in this article, such as altitude. First off, we need to add a new object to Google Maps Api v3 - the MarkerWithLabel object. This allows us to add text labels to Google Maps. They are also draggable. I have updated a Plunk below so you can see the end result yourself:

Location in Google Maps with altitude - Plunk

The MarkerWithLabel.js contains the additional javascript code to add the MarkerWithLabel object. We add the marker inside the showPosition method with the following code:


  function showPosition(position){
        
         var mapCanvas = document.getElementById("demo");
  var myCenter = new google.maps.LatLng(position.coords.latitude, position.coords.longitude); 
  var mapOptions = {center: myCenter, zoom: 12};
  var map = new google.maps.Map(mapCanvas,mapOptions);
  var marker = new google.maps.Marker({
    position: myCenter,
    animation: google.maps.Animation.BOUNCE
  });
  marker.setMap(map);
  
  console.log(position.coords);
  
  
   var image = 'https://developers.google.com/maps/documentation/javascript/examples/full/images/beachflag.png';
 
  

     var altitudeMarker = new MarkerWithLabel({
       position: myCenter,
       draggable: true,
       raiseOnDrag: true,
       icon: image,
       map: map,
       labelContent: position.coords.altitude.toString(),
       labelClass: "labels", // the CSS class for the label
       labelStyle: {opacity: 0.75}
     });
     
     
        
      }

We add the altitude, using the position.coords.altitude object.

A good tip here is to add high accuracy of the GeoLocation.


  function getLocation() {
    

    var geo_options = {
     enableHighAccuracy: true, 
     maximumAge        : 30000, 
     timeout           : 27000
    };


         if (navigator.geolocation){
          var position = navigator.geolocation.getCurrentPosition(showPosition, null, geo_options);
        }
      }



Note that the client has got to have a positioning device supporting returning the altitude. Most smartphones today got GPS for example.
As a test - you can change the value displayed to position.coords.accuracy.toString() instead. Accuracy is always return in the Coords object.

Sunday, 17 September 2017

HTML 5 Geolocation introduction

This article will introduce you to HTML 5 Geolocation API.

First off, test the browser for support of HTML 5 Geolocation. The first call to get the location of the client / user will also prompt a dialog that the user must usually confirm to to allow getting the location.
The following Javascript is necessary to get the latitude and longitude of the client :

 function getLocation() {
  if (navigator.geolocation){
   var position = navigator.geolocation.getCurrentPosition(showPosition);
  }
 }
        
 function showPosition(position){
  console.log(position);
  $("#demo").html(position.coords.latitude + " " + position.coords.longitude);
 }








Note that you can retrieve additional information such as altitude, heading and speed if the client got positioning hardware supporting this.
Mozilla Developer Network - Coordinates object
In Firefox, you have to use HTTPS to use Geolocation in newer versions of this browser. The client must agree to share the current location. A demo of Geolocation is here:

HTML 5 Geolocation demo - Plunk

Let us also use a map to show the location of the user. We can use Google Maps API. To use this API, request a Google API Key from here:

Google API Key site

We plot the current location with some script below using the Google Maps API, adding a Marker that is bouncing on top of the current location.

  function getLocation() {
   if (navigator.geolocation){
    var position = navigator.geolocation.getCurrentPosition(showPosition);
   }
  }
        
  function showPosition(position){
        
   var mapCanvas = document.getElementById("demo");
   var myCenter = new google.maps.LatLng(position.coords.latitude, position.coords.longitude); 
   var mapOptions = {center: myCenter, zoom: 12};
   var map = new google.maps.Map(mapCanvas,mapOptions);
   var marker = new google.maps.Marker({
    position: myCenter,
    animation: google.maps.Animation.BOUNCE
   });
    marker.setMap(map);
        
  }
      



The current location is displayed using Google Maps as displayed here:



Support for Geolocation in Firefox is limited to HTTPS and recent version of Firefox may not function with Geolocation in Linux, newer than Firefox version 20. If so, downgrade to Firefox Version 20. I have tested the code above using Opera web browser in Linux Mint 15.

Note that we here added Google Maps Javascript source reference and an Google API key.





  <script src="https://maps.googleapis.com/maps/api/js?key=AIzaSyAeymq4mlrbKoBUhU3LdegaudQDnY7MFPo&callback=myMap"></script>
  



Saturday, 2 September 2017

Modernizr feature discovery demo

I just made a Modernizr feature discovery demo! It lists up the features Modernizr looks for and tests the browser you are running if it supports that feature! Plunk - Modernizr demo




<html class="no-js">

<head>
<meta charset="utf-8"/>
<title>Modernizr browser feature detection</title>
<script data-require="modernizr@*" data-semver="2.6.2" src="//cdnjs.cloudflare.com/ajax/libs/modernizr/2.6.2/modernizr.js"></script>
<script data-require="jquery@*" data-semver="3.1.1" src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<script data-require="underscore.js@*" data-semver="1.8.3" src="//cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>
</head>

<style>

.greenlight {

}

.yellowlight {

}

.redlight {

}

.trafficlight {


}

.trafficlight:after {
    background-color: #10AF20;
 border-radius: 10px;
 padding-left: 5px;
 padding-right: 5px;
}

.redlight:after {
 content: "UNSUPPORTED ";
    color: #f0f0af;
    background-color: #AF1020;
}

.yellowlight:After {
 content: "PERHAPS SUPPORTED";
 color: #f0f0af;
    background-color: #AFAF10;
}

.greenlight:after{
 content: "SUPPORTED ";
 color: #f0f0af;
 background-color: #10AF20;
}

.underlight{
 margin-left:30px;
}

li {
 font-family: Trebuchet, Verdana;
 margin: 4px;
}

</style>

<body>
<h2>Modernizr browser feature detection</h2>


<ul id="ModernizrFeatureList">
<script>

function displayfeature(feature, isSubfeature){
   var isFeaturePartiallySupported = false;
   var isFeatureSupported = false; 
   if (eval("Modernizr." + feature) === true){
    isFeatureSupported = true;
   }
   if ((eval("Modernizr." + feature) === "probably") | (eval("Modernizr." + feature) === "maybe")){
    isFeaturePartiallySupported = true;
   }

   //debugger;

   var trafficlight = "trafficlight" + " ";
   if (isFeatureSupported)
    trafficlight += "greenlight"; 
   if (isFeaturePartiallySupported)
    trafficlight += "yellowlight"; 
   if (!isFeatureSupported && !isFeaturePartiallySupported){
    trafficlight += "redlight";
   }

   if (isSubfeature)
    trafficlight += " underlight";

   var featureToShow = "<li class='" + trafficlight + "'>" + feature + ": " + eval("Modernizr." + feature) + " </li>";

   return featureToShow;
}

var modernizrProps = _.sortBy(Object.keys(Modernizr), function(key){ return key; });


modernizrProps.forEach(function(feature, index){

  var modernizrFeatureType = eval("typeof Modernizr." + feature); 

   if (modernizrFeatureType == "boolean"){
     var f = displayfeature(feature, false);
     $("#ModernizrFeatureList").append(f);
   }
   else if (modernizrFeatureType === "object"){
    try {
     //debugger;
     for (var subfeature in  eval("Modernizr." + feature)){
     var subf = displayfeature(feature + "." + subfeature, true);
     $("#ModernizrFeatureList").append(subf);
    }

    }
    catch (Error){

    }
   }
 
});


</script>

</ul>
</body>
</html>