4 ms·
> They never had positional information, except by virtue of the timing signals for those data points to their satellite. Does anyone have any more insight in
by nly 13y ago
> They never had positional information, except by virtue of the timing signals for those data points to their satellite.
Does anyone have any more insight in to this? Was the protocol a one-way ping, or a ping-pong exchange? Previous reports have inferred that the data from the hourly pings were incredibly basic. Obviously timing signal propagation is the basis for GPS, but is it normal or even feasible to collect millisecond or microsecond transmission timings for engineering data fed via satellites like the ones operated by Inmarsat? What other variables would have been used for ranging?
1 millisecond at the speed of light is close to 300km.
- foobarqux 13y agoI thought the distance measurement was derived from received signal strength. edit: Other's have said that they are using Doppler shift.
- sateesh 13y agoThis story from Telegraph is scanty in details. But it also mentions Doppler effect. http://www.telegraph.co.uk/technology/news/10719304/How-British-satellite-company-Inmarsat-tracked-down-MH370.html http://www.telegraph.co.uk/technology/news/10719304/How-Brit...
- nly 13y ago> These pings from the satellite – along with assumptions about the plane’s speed – helped Australia and the US National Transportation Safety Board to narrow down the search area to just 3 per cent of the southern corridor on 18 March So it looks like the announcement today is actually old news. In any case, it's not entirely clear to me how the Doppler effect would distinguish between northerly and southerly passage.
- DrJokepu 13y agoMaybe it could be used to establish whether the airplane is getting closer to or getting further away from a satellite? Maybe even the relative speed?
- berkut 13y agohttp://www.pprune.org/rumours-news/535538-malaysian-airlines-mh370-contact-lost-356.html#post8393194 http://www.pprune.org/rumours-news/535538-malaysian-airlines...