Companies such as Apple and Google must explicitly gain consent from users before tracking the location of their mobile device, according to an influential European privacy group.
The Article 29 Working Party, a group of European privacy authorities, said that geolocation data is personal and that permission for collecting it cannot be given through people accepting terms and conditions.
In an advisory document (PDF) published on Monday, the group looked at the application of the EU's Data Protection Directive and the e-Privacy Directive to the gathering of geolocation data via GSM base stations, GPS and Wi-Fi. It noted that this data is being used by companies to sell a variety of location-based services, such as maps and navigation, augmented reality and local advertising.
"If telecom operators want to use base-station data in order to supply a value-added service to a customer, according to the revised e-Privacy Directive they must obtain his or her prior consent," the group said. "They must also make sure the customer is informed about the terms of such processing."
Since smartphones and tablet computers are inextricably linked to their owner, the movement patterns of the devices provide a very intimate insight into the private life of the owners.– Article 29 Working Party
The Article 29 Working Party said that consent should not be gained through general terms and conditions; rather, people must explicitly agree for their data to be used for a specified purpose. Companies must also only use geolocation when necessary, and allow employees to switch off geolocation outside work.
"Since smartphones and tablet computers are inextricably linked to their owner, the movement patterns of the devices provide a very intimate insight into the private life of the owners," said the group. "One of the great risks is that the owners are unaware they transmit their location, and to whom."
The group said that companies must make it clear that location tracking is taking place even if a person is using a service that needs to have tracking constantly switched on.
"In order to prevent the risks of secret monitoring, the Article 29 Working Party considers it essential that the device continuously warns that geolocation is 'ON', for example through a permanently visible icon," it said.
Apple and Google have recently come under scrutiny for their use of location tracking in mobile devices. In April, researchers revealed iPhones and iPads running iOS 4 record user location and movements via a database of base station co-ordinates and time stamps. Consent for the data collection was given via a terms-and-conditions document.
The Article 29 advisory document comes as US government bodies begin inquiries into geolocation tracking. Apple and Google have appeared before Senate sub-committees twice in May, and both have been invited to a public forum in June to discuss the topic.
Get the latest technology news and analysis, blogs and reviews delivered directly to your inbox with ZDNet UK's newsletters.