GPS signals will be jammed in the autumnWalkers in mid Wales who rely on GPS for navigation should make a note in their diary.

GPS signals will be jammed in the autumn

The military will be conducting jamming exercises around its Sennybridge training area in September and October. This means global-positioning systems may not work for periods during the exercise.

So you’d better dig out your map and compass if you’re doing any serious navigation in the area from Monday 22 September until the following Friday. A similar operation will take place, this time for 12 days, starting Monday 13 October.

Ofcom, which regulates radio communications in the UK, issued a warning today about the exercises at the MoD training area, between Llanwrtyd Wells and Brecon, about 8km (5 miles) north of the Brecon Beacons national park. The jamming will last for bursts of three minutes up to three hours a day, between 8am and 5pm in September, and 9am and 5pm in October.

Mountain rescuers recommend walkers should always have manual methods of navigating anyway, even when carrying GPS receivers, which can be temporarily affected by thick forestation, cliff faces and other obstacles, all of which can either cut out the signal or make it less accurate.

The Global Positioning System is an American network relying on up to 32 orbiting satellites to transmit navigation signals capable of being picked up by receivers on the earth’s surface. Although originally designed for military use, it is now widely available to civilians, both with hand-held receivers such as used by walkers, and in car satellite-navigation system.

Walkers who need information can ring 07766 134520, while the exercise is running.