Apple on Monday told US lawmakers that it gathers location information from some users every 12 hours.

The company collects GPS (global positioning system) data daily from iPhones running OS 3.2 or iOS 4, the iPad manufacturer said in a 13-page reply to questions posed by Representatives Ed Markey from Massachusetts and Joe Barton from Texas.

The Congressmen sent the questions to Apple after the Los Angeles Times reported changes in Apple's general privacy policy about location information. However, the changes had already been included in terms-of-use documents for specific Apple products.

The company said it uses the data to analyse traffic patterns and density. It collects such data from customers who have approved the use of location-based services on the phone.

"While I applaud Apple for responding to our questions, I remain concerned about privacy policies that run on for pages and pages," Barton stated.