>> GPS is an adjunct to navaids and charting Maybe 15 years ago. Today, GPS is the primary and charting comes slower/later to confirm positions. GPS isn't do

>> GPS is an adjunct to navaids and charting Maybe 15 years ago. Today, GPS is the primary and charting comes slower/later to confirm positions. GPS isn't done intermittently. It is just on 24/7. Then occasionally (on the order of minutes to hours) a ship's position is confirmed by other means if possible. Near land the crew will sight landmarks to confirm the GPS track is accurate. But go onboard a ship in bad weather at night. You won't see the captain out there with a sextant trying to track stars. The GPS is basically it until there is good reason to second guess or confirm its accuracy. If the GPS fails, the ship's insurer might just tell the ship to hold position until it gets fixed. Ships are not planes. They can actually stay away from land/danger for days/weeks while repairs happen.