Europe has yet to fully wake up to the danger of maritime disasters caused by signal jamming and blackouts of satellite navigation devices, say the proponents of a back up system on trial in British and Dutch ports. Ships increasingly rely on systems that employ satellite signals to find a location or keep exact time including the Global Positioning System (GPS) and GLONASS. But experts say such systems are vulnerable to signal loss from solar weather effects or radio and satellite interference and can also be affected by intentional jamming by criminal gangs, nation states or potentially from militant groups. The General Lighthouse Authorities of the UK and Ireland (GLA) is pioneering a radio-based back-up prototype called eLoran.