
Analysis of suspected MH370 pings recorded by Ocean Shield - ntakasaki
http://iheartmatlab.blogspot.com.au/2014/04/analysis-of-suspected-mh370-pings.html
======
JonnieCache
More DIY youtube-video-telemetry-data-extraction fun from the illustrious Oona
Räisänen:

[http://www.windytan.com/2014/02/mystery-signal-from-
helicopt...](http://www.windytan.com/2014/02/mystery-signal-from-
helicopter.html)

She actually pulls out data from a binary stream. Her whole blog is amazing,
it's been on here many times.

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apaprocki
The potential Doppler shift is mentioned at the end. If there were three towed
ping detectors and all of them were moving at a fixed speed, would you be able
to immediately triangulate the position of the device? How many seconds of
ping would you need in order for it to be reliable? I wonder if the software
to do that (I guess it must exist) has a very clean UI showing approximate
location getting better as more data flows in. (Think the indicator for GPS
accuracy in map apps.)

~~~
ISL
You can do better than Doppler shift. If the clocks on three ping detectors
are well-synchronized and their locations known, you can use the ping arrival
times to triangulate. Sound propagation in water is nontrivial, but the people
who are good at it are good at it.

Furthermore, as long as the clock on the pinger is fairly good, the ocean
environment fairly stable, and you don't drop many pings, you can drive one
ping detector around and triangulate from the ensemble of ping measurements.

~~~
vonmoltke
You can do that with a single moving platform, since the target is not moving.
Record the bearings for half an hour, make a 90° turn, and recore another half
hour of bearing data. That should give a decent approximate location. Its also
basic target motion analysis that a military sonar operator can do in their
sleep.

~~~
toomuchtodo
> Its also basic target motion analysis that a military sonar operator can do
> in their sleep.

Which makes me wonder: Does the US not have military assets in the area? Or do
they and they don't want to disclose their capabilities?

EDIT: I'm behind the times; I didn't know the US had a sub-hunter in the area.

~~~
cube13
I think it's safe to assume that someone(US, Russia, China, etc.) has
_something_ in the area, but nobody's going to be talking about it to the
public.

It's not so much about disclosing capabilities as much as it's just simply
operational secrecy. The entire point of a submarine is that it's hard to
find.

~~~
trhway
>I think it's safe to assume that someone(US, Russia, China, etc.) has
something in the area

accidentally, this search may find a lot of that "something"

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sabman
Best would be to contact the video source and ask exactly what the audio track
is.

I don't think the video shows the pings from the blackbox. More likely they
are the chirp pings from a sidescan sonar. They are looking for an shadow
(image) of the blackbox in the data. Here is a nice diagram showing what they
are looking for:
[http://www.southwestcoastalgroup.org.uk/cc_mon_sidescan.html](http://www.southwestcoastalgroup.org.uk/cc_mon_sidescan.html)

~~~
thommo101
The video shows a moving spectrogram of the received signal from the TPL-25
towed pinger locator. It has nothing to do with sidescan sonar.

In fact they explicitly have not launched the sidescan capable Bluefin21 AUV
because of fears of acoustic contamination of the towed pinger audio.

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acqq
According to the Wikipedia, the cockpit voice recorder records only up to last
two hours of the talks in the cockpit:

[http://en.wikipedia.org/wiki/Flight_recorder#Cockpit_voice_r...](http://en.wikipedia.org/wiki/Flight_recorder#Cockpit_voice_recorder)

It appears that even once the recorder is found we can just discover that
nobody talks anything substantial in the last two hours of the long flight,
that is, that "interesting" (to find the motives) conversations are already
overwritten.

The flight data recorder can save more flight data but maybe it can only be
the confirmation of the flight path already relatively known. Maybe the
mystery won't be solved even with these devices present?

~~~
walls
Would there be any chance of recovering data from personal phones/laptops?
Assuming the passengers were alive and aware, perhaps some of them tried to
document what happened.

~~~
Shank
The only problem with that idea is that electronic devices may have been
scattered on the ocean floor or not survived fire or other destructive forces
that happened either during flight or during landing.

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cynwoody
I find it annoying that the media call this thing a "pinger". To ping means to
send out a signal in expectation of maybe receiving an echo or reply. It's a
two-way process. The device's manufacturer calls† their product a beacon
because that's what it is. It doesn't listen. It only sends. Until its battery
runs out.

Arguably, a _real_ pinger (underwater transponder?) would have much better
battery life, needing only to listen for part of each second or minute for a
page from a passing search vessel. It would squawk only when it hears such a
page, and, encoded within the squawk would be the airplane's serial number, so
there would be no doubts about marine mammals or stray locators. Also, the
search vessel could measure the ping delay, revealing the range to the wreck.
A number of pings from different positions would pinpoint the wreck's
location.

The pinger could listen for search vessel pages on one frequency and respond
on another. The page could contain a serial number, which the pinger would
echo back. So, it would be simple to match page and response for the delay
time measurement.

†[http://www.radiantpowercorp.com/dukane-seacom-locator-
beacon...](http://www.radiantpowercorp.com/dukane-seacom-locator-beacons.aspx)

~~~
kevinchen
I worked on a project involving this type of underwater audio beacon, and
everyone called it a "pinger." So it's not just the media.

~~~
prescindor
The GP's point is well-taken. The company that produces this particular widget
calls it an "underwater locator _beacon_ ",[1] not a "pinger".

To "ping" implies you are the locator, not the locatee, whether you are
sitting in front of a terminal window or are running the _active_ sonar[2] on
a boat. You send a signal out and await a response, be it a reply (as in the
case of the ping command) or an echo (as in the case of sonar).

[1][http://www.radiantpowercorp.com/dk-series-underwater-
locator...](http://www.radiantpowercorp.com/dk-series-underwater-locator-
beacons.aspx)

[2][http://en.wikipedia.org/wiki/Sonar#Active_sonar](http://en.wikipedia.org/wiki/Sonar#Active_sonar)

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arh68
Re: low battery, what's that circuit look like? I can imagine a real simple RC
discharge/charge circuit (ping/delay) that would behave like that. Of course
anything quartz-based would behave very differently.

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ape4
Why no radio ping?

~~~
ISL
Deep ocean water is opaque to all but the lowest frequency RF.

[http://en.wikipedia.org/wiki/Extremely_low_frequency](http://en.wikipedia.org/wiki/Extremely_low_frequency)

~~~
cynwoody
Which is why, during the Cold War, the US maintained very powerful long wave
transmitters, both land-based and airborne. Using VLF†, they could send the
nuclear launch codes to the nuclear missile submarines without the subs having
to break the surface and create a possible radar return.

They kept an airplane aloft 24 hours a day carrying a SAC general. In the
event of war, it could reel out a long-wire antenna a couple of miles long
from its tail and send out the codes.

†[http://en.wikipedia.org/wiki/Communication_with_submarines#V...](http://en.wikipedia.org/wiki/Communication_with_submarines#Very_low_frequency)

~~~
eitland
I wonder how this can have worked; according to my understanding VLF
transmission for underwater reception needs very much power.

Did they bring really a powerful generator in the plane?

~~~
brc
[http://en.wikipedia.org/wiki/Naval_Communication_Station_Har...](http://en.wikipedia.org/wiki/Naval_Communication_Station_Harold_E._Holt)

This says 1 MW power.

I would say a mobile platform could get away with much lower power.

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vondur
I thought the audio frequency that was chosen for the black boxes was one that
only came from a man made source?

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dalek2point3
its too bad that the data from the search process is not made available more
openly. they used crowdsourdcing for the image analysis, but as this analysis
shows -- its likely the people can really be useful at all stages of the
search effort.

kudos for doing this! really great.

~~~
cshimmin
All he did was take an average of the pinging interval... I'm pretty sure the
analysts actually working on this didn't need to crowdsource that.

~~~
tehaaron
In the OPs defense, he not only determined the average ping interval but also
provided analysis on what the numbers could mean...without the second part,
the numbers don't matter.

I would hope the people working this case could do the same but I also support
the idea of crowd-sourcing.

~~~
jlgaddis
It sounds like a good idea in theory but, in reality, I think you'd end up
with a lot of people coming to different conclusions, all convinced that they
are right.

The "crowdsourcers" would be demanding that their theories be looked into and,
if they were, it would take away from the search operation vital resources.

It reminds me of when I'm troubleshooting network issues and my (very non-
technical) boss calls and offers up his ideas of what might be wrong. It
distracts me from what I'm doing and simply results in it taking longer to
resolve the issue.

