Re:China's GPS 'rival' Beidou
by tialaramex on Monday October 22, 2018 @03:23PM
(#18277517)
I suspect this is either a misunderstanding or just copy-pasted from descriptions of a different earlier system.
It doesn't make any sense to have the ground station transmit to figure out its location. To give a baseline, that's how the original analogue COSPAS SARSAT worked last century, using doppler measurements to get a location over time - and its accuracy was appalling, a human operator has to use equipment to narrow down where the signal is, it takes significant time to get a 1 nautical mile search area. Which is much better than "I dunno, in the sea?" for a lost ship or plane, but you're still going to need a serious search-and-rescue operation to find anybody.
A modern digital COSPAS SARSAT system you may have seen if you're a serious hiker or outback flyer just does GPS, it uses GPS to figure out where it is, then sends a digital signal that says "I need help, here are my GPS co-ordinates" hence the slogan "Taking the search out of search and rescue".
It doesn't make any sense to have the ground station transmit to figure out its location. To give a baseline, that's how the original analogue COSPAS SARSAT worked last century, using doppler measurements to get a location over time - and its accuracy was appalling, a human operator has to use equipment to narrow down where the signal is, it takes significant time to get a 1 nautical mile search area. Which is much better than "I dunno, in the sea?" for a lost ship or plane, but you're still going to need a serious search-and-rescue operation to find anybody.
A modern digital COSPAS SARSAT system you may have seen if you're a serious hiker or outback flyer just does GPS, it uses GPS to figure out where it is, then sends a digital signal that says "I need help, here are my GPS co-ordinates" hence the slogan "Taking the search out of search and rescue".