Before satellite navigation (GNSS) was available for civilian aviation, the requirement for large land-based navigation aid (NAVAID) facilities generally limited the use of instrument approaches to land-based (i.e. asphalt, gravel, turf, ice) runways (and those on aircraft carriers). GNSS technology allows, at least theoretically, to create instrument approaches to any point on the Earth's surface (whether on land or water); consequently, there are nowadays examples of water aerodromes (such as Rangeley Lake Seaplane Base in Maine, United States) that have GNSS-based approaches.