How exactly does geolocation work in browsers

Determine the location in the browser using the HTML5 Geolocation API

All browsers that no longer date from the digital stone age (Internet Explorer 9, Firefox 3.5 and Google Chrome) are able to use the geolocation API officially provided by the W3C to provide information about the location of the User is located.

How is the location determined using the geolocation API?

The location determination via HTML5 is relatively complex and mature and goes through a number of steps to determine with increasing accuracy:

  1. IP address
  2. WiFi networks
  3. Radio signals (cellular network)
  4. GPS transmitter (only with 'enableHighAccuracy')

The determination of the location works very precisely if the user has a GPS transmitter in his device. Of course, this is practically never the case with stationary PCs; However, every common smartphone nowadays has a GPS module and can thus provide an exact position determination - also to the browser. Information from the WLAN and cellular network is also used if no GPS data is available. Only in the worst case does the browser access the IP address, which however can have an inaccuracy of 50-100km due to the use of dial-in nodes.

Determine current location with getCurrentPosition ()

Access to the Navigator object (window.navigator) is sufficient to initiate the determination of the position:

The "position" object has the following properties:

PropertyTypeinfo
doubleDegree
doubleDegree
double or meter
doublemeter
double or meter
double or Degrees clockwise from north
double or Meter / sec.

 

Example of location determination with HTML5 geolocation

When loading this page, the browser asked you whether you would like to allow selfhtml5 to determine your location. This dialog is browser-dependent and (currently) looks like this in FireFox, for example:

Depending on whether you have given your consent to the location determination or not, your position or an error message will appear in the following box.

Your position data determined by the browser

lat
lon
altitude
accuracy

 

And here is the code for the geolocation example

 

How accurate is position determination via geolocation?

As we have seen, geolocation API makes it easy to find your location. It gets a little more exciting when we have higher demands on the accuracy of the measurement data.

As can be seen in the table above, the position object already provides an accuracy, the “accuracy” in meters, which is intended to quantify the maximum possible deviation. The results of this attribute can be very different depending on the device used. In this context, it is also important whether the geolocation should be determined with a high degree of accuracy (enableHighAccuracy), as described in the next chapter.

The following are the typical accuracies of geolocation determination:

Device typeaccuracy
Pc2,000-140,000m
Smartphone without GPS20-80m
Smartphone with GPS5-20m (with enableHighAccuracy)

Location determination with high accuracy through "enableHighAccuracy"

If you want to determine a very precise location, you still need GPS according to the current state of the art. The useful chips are now built into all modern smartphones and are therefore basically an excellent choice for determining your location, if there were not some restrictions to be observed:

  • GPS tracking is energy-intensive and significantly reduces battery life
  • Positioning via GPS requires an initialization phase of up to 15 minutes if it has been a long time since you last used GPS before results are available. In everyday smartphone life, however, relatively current satellite data is often available and the measurement usually takes between 10 and 30 seconds.
  • The user may have to agree to the exact location determination one more time, as there are separate rights in browsers as well as iOS and Android

If, despite these restrictions, it is sensible or necessary to determine the location via GPS, the use of the GPS module can be made by transferring the parameter enableHighAccuracy to be activated:

Problems with the HTML5 geolocation determination

The W3C stipulates that the location may only be determined with the express consent of the user. The browser providers have implemented this accordingly - this means that, depending on the browser, a warning message pops up or is inserted under the address line (sometimes difficult to see) and asks the user whether he would like the location data to be determined make sure to point out at the appropriate point that the service only works after acceptance of the location transfer.

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