"Checking-in" – a process once associated with airports and hotels has taken on a whole new meaning in the last year or so.

More and more of us use a wide range of electronic devices to check-in on our social networking websites of choice such as Facebook, Twitter or Foursquare to let all our friends know exactly where we are and what we are doing there. However, be warned, this "location data" is not just being seen by your friends.

A study carried out by two North American universities revealed that a staggering 95% of mobile phone users can be identified from their location data alone and (even more surprisingly) it only takes 4 pieces of time and location data to do it.

The research parallels a study conducted in the 1930's which revealed that you only need 12 points to identify a fingerprint. Similarly, it is thought that human movement is so unique and limited in scope that it acts almost like a fingerprint and accordingly, as an identifier.

Location data does not reveal personal information such as names, addresses or telephone numbers but if the user's movement pattern is unique then it may be possible to use other information to link the data back to them individually.

Whether or not this type of personal data is anonymised, it is becoming increasingly available. If you have a mobile its position can be traced even when it is switched off! This location data can then be used by third parties to drive services and target advertisements to you. Companies who provide mobile phone networks or applications also collect data from mobile phone users and release it as "anonymised" or "aggregated data sets".

Location Data, "Big Data" & Privacy

Most of us give up location data voluntarily through Facebook check-ins or geo-located Tweets and because everyone is doing it, it is not viewed as personal data likened to Tweeting your bank details. Accordingly, it is seen as "low resolution" data (low sensitivity). However, low resolution data may actually be or become "high-resolution" data the more available it becomes, and as mobile phone networks become aware of its value.

The increasing value of "Big Data" to service providers and advertisers has sparked the utility/anonymity trade off debate begging the complex question – does the use of Big Data outweigh the impact its use may have on the privacy of individuals?

It is thought that the collection and use of Big Data can benefit the wider public as it is being used to drive and enhance services. The replacement of the trusted road atlas by the Sat-Nav is a classic example of location data from mobile phones being used to improve traffic reporting through the use of anonymised data to calculate how fast users are moving on a stretch of road.

However, the crux of this is the potential for data to be de-anonymised and this poses a concern to privacy organisations. Personal Data under the Data Protection Act 1998 does not include anonymised data but once it is de-anonymised this changes everything and therefore does pose a risk to users. 

In light of the proposed Data Protection Regulations from Europe, this is very much a "watch this space" moment in time.