7 ms·

Analysis of suspected MH370 pings recorded by Ocean Shield

186 points by ntakasaki 13y ago

dalek2point3 13y ago
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 13y ago
  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 13y ago
    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 13y ago
      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.
ape4 13y ago
Why no radio ping?
- ISL 13y ago
  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
  - deleted 13y ago
    [deleted]
  - cynwoody 13y ago
    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#Very_low_frequency http://en.wikipedia.org/wiki/Communication_with_submarines#V...
    - eitland 13y ago
      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 13y ago
        http://en.wikipedia.org/wiki/Naval_Communication_Station_Harold_E._Holt http://en.wikipedia.org/wiki/Naval_Communication_Station_Har... This says 1 MW power. I would say a mobile platform could get away with much lower power.
      - cynwoody 13y ago
apaprocki 13y ago
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 13y ago
  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 13y ago
    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 13y ago
      > 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.
      - deleted 13y ago
        [deleted]
JonnieCache 13y ago
More DIY youtube-video-telemetry-data-extraction fun from the illustrious Oona Räisänen: http://www.windytan.com/2014/02/mystery-signal-from-helicopter.html http://www.windytan.com/2014/02/mystery-signal-from-helicopt... She actually pulls out data from a binary stream. Her whole blog is amazing, it's been on here many times.
sabman 13y ago
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
- kevinchen 13y ago
  Doubtful; why would they be worried about the black box pinger's battery running out then? Also, it's much easier to listen for the pings than to look for visual indication, since the pings can be analyzed by DSP software.
- thommo101 13y ago
  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.
deleted 13y ago
[deleted]
vondur 13y ago
I thought the audio frequency that was chosen for the black boxes was one that only came from a man made source?
cynwoody 13y ago
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-beacons.aspx http://www.radiantpowercorp.com/dukane-seacom-locator-beacon...
- benjamincburns 13y ago
  In college our underwater acoustics prof used an old copy of the Navy sonar manual to teach some fundamental concepts early on in the course. One of my favourite passages was when the Navy manual definitively answers the question of "if a tree falls in the forest and nobody's around to hear it, does it make a sound?" The answer, according to the Navy is that no - in order for a sound to exist there must be both a transmitter and a receiver component, and if both are not present then the energy emitted by the lone transmitter does not constitute "sound." So, according to that - you're both right in that it's a two party process. However, I believe the term is appropriate in underwater acoustics for anything which dumbly sends out a relatively predictable signal on a regular interval.
- blantonl 13y ago
  The problem here is designing a microphone that is sensitive enough to listen for a page from a passing search vessel and also survive the crash.
- kevinchen 13y ago
acqq 13y ago
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_recorder http://en.wikipedia.org/wiki/Flight_recorder#Cockpit_voice_r... 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?
- TomGullen 13y ago
  FDR records huge array of instruments, this data alone has solved countless crashes.
  - acqq 13y ago
    I'm afraid there's still chance that we'll learn exactly when it crashed etc but not why all this happened if it was really the result of somebody doing something intentionally and everything important happened before the last two hours. The current estimates are already that the plane simply flew on autopilot during the last hours. It's possible that nobody spoke in the cockpit at that time.
    - brc 13y ago
      It's unlikely that no noise at all was recorded in the cockpit. Other issues have been discovered from non-voice recorded noises - like the 737 Rudder failure problem that was deduced from the noise of a pilot grunting as he tried to move the rudder.
    - Perdition 13y ago
      The FDR data will still tell them whether it flew (ie pilot commanded) into the water or crashed (ie ran out of fuel or suffered engine failure), whether it had been on autopilot, whether there was an earlier fire that knocked out communication and navigation etc. There are plenty of events where the CVR provided no useful information and the cause of the crash was determined by the FDR.
arh68 13y ago
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.

186 points by ntakasaki 13y ago

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 13y ago
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 13y ago
  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 13y ago
    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.

ape4 13y ago

Why no radio ping?

ISL 13y ago
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
- deleted 13y ago
  [deleted]
- cynwoody 13y ago
  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#Very_low_frequency http://en.wikipedia.org/wiki/Communication_with_submarines#V...
  - eitland 13y ago
    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 13y ago
      http://en.wikipedia.org/wiki/Naval_Communication_Station_Harold_E._Holt http://en.wikipedia.org/wiki/Naval_Communication_Station_Har... This says 1 MW power. I would say a mobile platform could get away with much lower power.
    - cynwoody 13y ago

apaprocki 13y ago

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 13y ago
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 13y ago
  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 13y ago
    > 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.
    - deleted 13y ago
      [deleted]

JonnieCache 13y ago

More DIY youtube-video-telemetry-data-extraction fun from the illustrious Oona Räisänen: http://www.windytan.com/2014/02/mystery-signal-from-helicopter.html http://www.windytan.com/2014/02/mystery-signal-from-helicopt... She actually pulls out data from a binary stream. Her whole blog is amazing, it's been on here many times.

sabman 13y ago

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

kevinchen 13y ago
Doubtful; why would they be worried about the black box pinger's battery running out then? Also, it's much easier to listen for the pings than to look for visual indication, since the pings can be analyzed by DSP software.
thommo101 13y ago
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.

deleted 13y ago

[deleted]

vondur 13y ago

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

cynwoody 13y ago

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-beacons.aspx http://www.radiantpowercorp.com/dukane-seacom-locator-beacon...

benjamincburns 13y ago
In college our underwater acoustics prof used an old copy of the Navy sonar manual to teach some fundamental concepts early on in the course. One of my favourite passages was when the Navy manual definitively answers the question of "if a tree falls in the forest and nobody's around to hear it, does it make a sound?" The answer, according to the Navy is that no - in order for a sound to exist there must be both a transmitter and a receiver component, and if both are not present then the energy emitted by the lone transmitter does not constitute "sound." So, according to that - you're both right in that it's a two party process. However, I believe the term is appropriate in underwater acoustics for anything which dumbly sends out a relatively predictable signal on a regular interval.
blantonl 13y ago
The problem here is designing a microphone that is sensitive enough to listen for a page from a passing search vessel and also survive the crash.
kevinchen 13y ago

acqq 13y ago

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_recorder http://en.wikipedia.org/wiki/Flight_recorder#Cockpit_voice_r... 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?

TomGullen 13y ago
FDR records huge array of instruments, this data alone has solved countless crashes.
- acqq 13y ago
  I'm afraid there's still chance that we'll learn exactly when it crashed etc but not why all this happened if it was really the result of somebody doing something intentionally and everything important happened before the last two hours. The current estimates are already that the plane simply flew on autopilot during the last hours. It's possible that nobody spoke in the cockpit at that time.
  - brc 13y ago
    It's unlikely that no noise at all was recorded in the cockpit. Other issues have been discovered from non-voice recorded noises - like the 737 Rudder failure problem that was deduced from the noise of a pilot grunting as he tried to move the rudder.
  - Perdition 13y ago
    The FDR data will still tell them whether it flew (ie pilot commanded) into the water or crashed (ie ran out of fuel or suffered engine failure), whether it had been on autopilot, whether there was an earlier fire that knocked out communication and navigation etc. There are plenty of events where the CVR provided no useful information and the cause of the crash was determined by the FDR.

arh68 13y ago

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.