Mobile phones and location tracking
Created | Updated Jun 5, 2002
The majority of the UK population is voluntarily carrying a neat little locator device - the mobile phone.
When switched on, a mobile finds a base station within range, normally but not always the closest. Your network then ‘knows’ more-or-less where you are. Every few minutes, your phone and the base station check you are still within range - you can hear this happening as stacatto interference on nearby audio equipment.
When you make or receive a call, the ‘cell ID’ of the base station you use is retained. Each of the network has several thousand base stations: O2, formerly known as BT Cellnet, had 6,600 when it was sold off by BT in 2001.
O2 says that for legal purposes, it can be sure that a phone is within 35 kilometres (22 miles) of the base station concerned. Vodafone operates the same kind of GSM 900 network, with the same range. Orange, T-Mobile (formerly One2One), and Virgin Mobile use GSM 1800 networks, which have half that maximum range.
But in practice, O2 has said it is confident of accuracy of 15 km (9 miles) in the countryside, and as little as 100 metres (330 feet) in cities. It has to be reasonably accurate, as this network operates location-based services including local traffic.
There are even microcells, with a radius as small as 50 metres, to cover a mobile hot-spot such as a tower block or a shopping centre, or ones positioned to cover a stretch of fast road rather than the streets below.
This cell ID location data is stored by your network for some time. Orange keeps it for 185 days, Vodafone for a year, O2 for at least a year, and Virgin Mobile plans to keep it for seven years, although it hasn’t been operational that long. T-Mobile won’t say.
All the networks say that only a few staff can see this data, although some journalists seem to have found ways around this: reported on here. The police can get hold of the data with an internally-issued warrant, as opposed to one issued by a judge.
Location data from mobiles has been used in high-profile court cases, such as the January 2002 conviction of Colm Murphy, for his part in the Omagh bombing of 1998. It was also used in the successful defence case at the Damilola Taylor murder trial, where the data suggested the defendants were two miles away.
In future, this location information is likely to be a lot more accurate. Third-generation mobiles are likely to include satellite-based technology which will locate the user to within a few metres world-wide, and are designed to be always on. So your network operator will have a very good idea of where you are and where you’ve been. Some plan to send you text-messages as they detect you passing certain shops.
You may wish to get hold of your own location data. I found this challenging when I attempted this for the Guardian (see story of 29 November 2001 below): Orange provided the numbers of the cells I had used, but not the location of the base stations. The networks are rarely keen to discuss the issue with the press: of the five main providers in the UK, only two have ever provided me with interviews, and one refuses to provide even basic information.
This is based on three articles I wrote for the Guardian's Online supplement, from 1 March 2001, 29 November 2001, and 28 March 2002. There are further relevant stories linked from my home page.
