[time-nuts] MH370 Doppler (Magnus Danielson)

Magnus Danielson magnus at rubidium.dyndns.org
Sat Aug 23 03:16:58 EDT 2014


Joe,

I did find it here:
http://www.dca.gov.my/mainpage/MH370%20Data%20Communication%20Logs.pdf

There is also some Inmarsat presentation giving a little more detail.

At the same time, the data gathered is from a system not designed for 
navigation and positioning purposes. It gives a rough hint. The reported 
resolution of the time and doppler and the checking time all gives that 
indication. The ring of last communication is from the time observation, 
and the reduction of that ring to likely sectors is due to doppler and 
time observations in previous observations trailing back to known 
position. Not very good hints. It's a system that only after the fact 
became a positioning system.

Doppler positioning is indeed possible, but that requires more 
continuous observations than once every hour.

I think that the Inmarsat folks most probably did about as much as you 
can with the data at hand.

The BTO jumps in 20 micro steps. That is 6 km of satellite-plane 
distance, which through geometry becomes wider as the angle from the 
satellite-earth-line increases. Good enough hint for a search party, but 
the lack of frequent "pings" only shows in what neighborhood to search. 
Making some assumptions on continuous flight path helps.

The BTO jumps between different types of channels, so only R-channel is 
being used for estimates.

This positioning problem isn't very complex, but is a good exercise as 
it is similar to the pseudo-range measurements and positioning from GPS.
The doppler and time observations with some basic geometry gives most of 
it out. The systematic doppler shift needs to be canceled but there is 
base measurements included that helps with that.

Cheers,
Magnus

On 08/23/2014 05:10 AM, Joe Leikhim wrote:
> You can probably find links to all of the data from the Duncan Steel Blog.
>
> You might start by looking at the questions the group has posed in an
> open letter to the ATSB and Inmarsat. Frankly, the data Inmarsat
> released appear to be rather scant and some believe to be doctored not RAW.
>
> I applaud those applying their rather extensive math skills at this
> problem, but from the outside, it appears to me that the problem is so
> very complex (error prone) and so many assumptions are being applied,
> that folks time would be better spent scouring the beaches for flotsam
> from the aircraft to wash up.
>
> But I could be wrong, maybe some time-nuttery will set them straight to
> an answer!
>
> It still bothers me that with all the space, ocean and ground based
> radar, sonar and imaging sensors, there is so little trace of the
> aircraft's travels that night. Somebody must have seen something. In
> fact some observers have reported seeing stuff, fire in the sky, low
> flying aircraft and even a fire bottle washed up on the beach in the
> Maldives, but so much stock is being put in the southward arc, that
> nobody is listening.
>
> "Does anyone has the set of timing and doppler measurements, and position
> of the observing satellite?
>
> Cheers,
> Magnus"
>



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