It is a vast military exercise designed to ensure Nato’s forces are in a state of preparedness.
But fishermen have warned a major UK-led training operation involving scores of warships, submarines and aircraft could jeopardise their safety at sea.
The 12-day-long operation Joint Warrior will see GPS navigation systems blocked across pockets of north-west Scotland when it begins next week.
As part of the operation involving the Army, Royal Navy and Royal Air Force, the denial of service will prevent electronic devices accessing satellite signals at Loch Ewe in Wester Ross and Faraid Head in Sutherland.
However, those who make their living in the seas of the Minch say the Ministry of Defence should have a rethink.
Austen Campbell, from Stornoway, who owns a prawn trawler, said: “The only thing the MoD have done is alert the coastguard to let them know around an hour before the signals are jammed, but that doesn’t help fishermen.
“If there was an emergency, you wouldn’t have a clue. They say that they would switch the jamming off if an incident did happen. but it’s still a great concern.”
Mr Campbell said that rather than conducting the jamming close to the Minch, Joint Warrior planners should venture further out to the west coast. “I don’t think those in charge understand what fishermen could face if the worst happened,” he added.
Ahead of the exercise, hillwalkers and mountaineers planning a getaway to the affected regions have also been warned not to rely on GPS systems, and instead use an ordnance survey map and compass to navigate.
The periodic GPS blackouts will take place for 12 days as of Monday. The denial of service will prevent all equipment from using GPS signals, including satnavs used by motorists. The blocks will be in place for up to a two hours at a time as the military carries out its manoeuvres.
The Royal Navy pointed out that detailed timings have been posted on the Queen’s Harbour Master Clyde section of its website, with details also advertised in the press. A spokesman said: “GPS jamming operations will take place at specific times and in a limited area in the northwest of Scotland during Joint Warrior. Mobile phone signals will not be jammed and contact with emergency services will still be possible.
“In preparation exercise planning staff have consulted with maritime, fishing, aviation and hill-walking organisations in order to make them aware of GPS jamming. This has resulted in a risk assessment to minimise the impact and to put in place robust procedures for any unforeseen eventuality.”