You’ve probably seen plenty of those targeting adverts that seem to know exactly where you are in the world. Google “pet shops” and it won’t display every pet shop in the world – it’ll show you the ones closest to you. Search for the weather, and you won’t see whether it’s snowing in Antarctica, you get the forecast for your area.
This is called “Geolocation” – the identification of the geographical location of an object, like your phone or your computer. The fact that the internet knows where you are can come as a surprise, considering that we live in a time of concern over internet privacy, worries over who can see personal data, and the right to be forgotten by search engines.
Yes – the internet knows where you’re accessing it from. This is very bad news if you’re looking up news of your supervillain schemes from your secret lair. But before you shout “You’ve betrayed me!” at your browser, take a look at our handy guide to understanding location tracking.
There are two ways that the internet can track your location, and your IP address provides the first. Whenever you browse a website, your computer tells it your IP address – a string of numbers that labels your device with a particular address. It functions exactly the way a street address does. When you surf the internet, it’s like sending a letter with an SAE included: you send out the request for the information, and the website sends its response to your computer.
“IP” stands for “Internet Protocal address”. The “Internet Protocol” is the way that the internet delivers information from one network to another, thereby creating an “internetwork” – a “network of networks”. If you dare, and have a thesaurus to hand, you can try deciphering the Wikipedia article about IP addresses.
If you type “IP address” into Google, it will tell you what your public IP address is. Your public IP address is what your router uses to communicate with the internet, but there are differences in how IP addresses work for different organisations. For example, your work IP address might stay the same, but your home address can change every three months or so, depending on your internet service provider, or ISP.
There are companies out there who have compiled databases which associate your IP address with an ISP, and that ISP with a geographic location. They’re usually spot on, but can be widely inaccurate. Neustar, Maxmind, IPligence and IP2location are all sites that offer IP address databases.
IP addresses aren’t the only way that the internet can find you. These days, your browser can try working out where you are, and will then send that location to the website you’re visiting. IP geolocation is a handy fall-back, but there are much more accurate ways of pinning your location down.
A desktop browser is liking to use your WiFi content, which is accurate to 20 metres, where IP Geolocation is only accurate on a city level (and can provide false positives). Mobile devices tend to use a digital version of an ancient technique – triangulation. In the physical world, triangulation has been used for thousands of years to measure distances, such as how far away ships are from a shore. In fact, Ancient Egyptian records from between 1803 and 1649 BC include use of triangulation to calculate the volume, surface area and the slope of different styles of pyramid.
GPS is a popular mobile triangulation technique. The “global positioning system” provides information on location and time to any position on Earth that has a line of site for four or more GPS satellites. GPS is accurate to 10 metres, but it only works when you’re outside. Another method is GSM/CDMA cell IDs, also known as CIDs, which means that your phone transmits the location of the nearest signal receiver that connects you to the internet. It works like that bit in crime dramas where they track a suspect down by locating the nearest signal tower to the last phone call, and it’s accurate to 1000m.
Rights to privacy
Before you panic about your privacy and assume your browser has betrayed you, though, it will have asked your permission before bombarding you with geographically-targeted adverts. But if you like a little internet conspiracy theory, add “The Traveller” from John Twelve Hawks’ Fourth Realm Trilogy to your Christmas list. “John Twelve Hawks” isn’t his real name, he doesn’t wish to confirm his identity, and he was so concerned about being findable that he dumped his browser back in 2006 and now lives “off the grid”!