SAN FRANCISCO – Researchers have discovered a disturbing pattern: dozens of ships whose GPS signals tell them they’re on land — at an airport no less — even when they’re far out to sea.

An investigation released this week by the Washington D.C.-based Resilient Navigation and Timing Foundation and Windward Ltd., a maritime data and analytics company, has found multiple instances of so-called GPS spoofing in Russian waters.

As recently as Monday, two vessels’ GPS told them they were at Sochi Airport near the site of the 2014 Sochi Olympics, 12 miles away from the harbor where the vessels actually were.

Researchers are calling these “mass GPS interferences” and they appear to be linked to the intentional transmission of false GPS signals to provide incorrect time or location information, possibly to veil certain facilities from attack.

Familiar to anyone using a smartphone or built-in auto navigation system to map out a route, the satellite-based system is also the main way ships and trucking fleets find their way.