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Tutorial
Locate the User's Position
The HTML Geolocation API is used to get the geographical position of a user.
Since this can compromise privacy, the position is not available unless the user approves it.
Note: Geolocation is most accurate for devices with GPS, like smartphone.
Using the Geolocation API
The getCurrentPosition() method is used to return the user's position.
The example below returns the latitude and longitude of the user's position:
EXAMPLE ❯
Handling Errors and Rejections
The second parameter of the getCurrentPosition() method is used to handle errors. It specifies a function to run if it fails to get the user's location:
EXAMPLE ❯
Displaying the Result in a Map
To display the result in a map, you need access to a map service, like Google Maps.
In the example below, the returned latitude and longitude is used to show the location in a Google Map (using a static image):
Example:
function showPosition(position) {
let latlon = position.coords.latitude + "," + position.coords.longitude;
let img_url = "https://maps.googleapis.com/maps/api/staticmap?center=
"+latlon+"&zoom=14&size=400x300&sensor=false&key=YOUR_KEY";
document.getElementById("mapholder").innerHTML = "<img src='"+img_url+"'>";
}
Location-specific Information
This page has demonstrated how to show a user's position on a map.
Geolocation is also very useful for location-specific information, like:
• Up-to-date local information
• Showing Points-of-interest near the user
• Turn-by-turn navigation (GPS)
The getCurrentPosition() Method - Return Data
The getCurrentPosition() method returns an object on success. The latitude, longitude and accuracy properties are always returned. The other properties are returned if available:
| Property | Returns |
|---|---|
| coords.latitude | The latitude as a decimal number (always returned) |
| coords.longitude | The longitude as a decimal number (always returned) |
| coords.accuracy | The accuracy of position (always returned) |
| coords.altitude | The altitude in meters above the mean sea level (returned if available) |
| coords.altitudeAccuracy | The altitude accuracy of position (returned if available) |
| coords.heading | The heading as degrees clockwise from North (returned if available) |
| coords.speed | The speed in meters per second (returned if available) |
| timestamp | The date/time of the response (returned if available) |
Geolocation Object - Other interesting Methods
The Geolocation object also has other interesting methods:
• watchPosition() - Returns the current position of the user and continues to return updated position as the user moves (like the GPS in a car).
• clearWatch() - Stops the watchPosition() method.
The example below shows the watchPosition() method. You need an accurate GPS device to test this (like smartphone):