INS accumulates error though. It comes in handy in the absence of any other navigation system, but generally an INS is supplemented by some sort of radio naviga

INS accumulates error though. It comes in handy in the absence of any other navigation system, but generally an INS is supplemented by some sort of radio navigation aid such as VOR, LORAN, or GPS to correct it. Except guess what! Many of the VOR stations in the USA have been shut down, due to the high availability of GPS!