The Boston Business Journal reports that Boston MedFlight helicopters have been cleared to use GPS to land in Boston, near Logan airport: “helicopter ambulance systems in New Hampshire and Maine have utilized GPS to land at hospitals, Boston MedFlight is the first in the country to use the technology in an area close to an airport, and in a city as big and busy as Boston.”

I was surprised because it hadn’t occurred to me that helicopters don’t use GPS.

I wrote back in 2010 when LORAN-C, the radio-based navigation aid for finding yourself at sea, was turned off because GPS superseded it. LORAN (“LOng RAnge Navigation”) used low-frequency signals (90 to 110 kilohertz). Ships at sea and aircraft could triangulate their position calculating the time delay of signals from two towers. Robust and cheap, it worked great – I learned about it when I got my private pilot’s license 30 years ago – but satellite-based GPS works even better, most notably by not being limited to within 1,000 miles or so of coastlines.

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