Re: [time-nuts] Aircraft ping timing
On Sat, 22 Mar 2014 07:40:27 - David J Taylor david-tay...@blueyonder.co.uk wrote: From: Hal Murray There is a newer system getting phased in: ADS-B http://en.wikipedia.org/wiki/Automatic_dependent_surveillance-broadcast The plane broadcasts it's position and velocity every second. The SDR folks are having fun with it. With one of the USB TV receiver gizmos and a Raspberry Pi, you are limited by the height of your antenna vs curvature of the earth. A friend with an antenna 20(?) feet up gets planes out to several hundred miles. I don't know how far it will work if you have an antenna on top of a hill. http://www.rtl-sdr.com/adsb-aircraft-radar-with-rtl-sdr/ == .. and by sharing this data on a central server you can overcome the line-of-sight limitation: http://www.satsignal.eu/raspberry-pi/dump1090.html There is a further development which may be of interest to the more mathematically oriented time-nuts, creating positions of aircraft which do no send out their position with ADS-B but use earlier responses. By comparing the timing of responses from aircraft which do send position with those that don't you can multilaterate a position for the position-less aircraft. This requires timing in the receiver device to a level of about 100 nanoseconds, most often achieved with a simple crystal oscillator (but which needs calibration). In the DVB-T sticks the usable sampling rate is about 2 MHz, and the resulting 500 microsecond resolution appears not to be good enough for even a basic multilateration fix. If anyone is interested further or could help with suggestions on improved accuracy with the DVB-T sticks, a suitable place would be the Plane Plotter Yahoo group: http://groups.yahoo.com/group/planeplotter/ Cheers, David Note that the ADS-B mentioned is just a fancy version of the transponder that was turned off. I ran into your R Pi page about halfway in the process of doing my Beaglebone Black RTLSDR page. I have RTLSDR and dump1090 running on Angstrom Linux. I bought the GPS you suggested and will attempt to get NTP going with it, so expect a question or two off line. ;-) I wonder if your problem with the timing is related to the R Pi being nearly maxed out. The Beaglebone Black is about 4x the processing power of the R Pi, with dump1090 running at 30% CPU. Seems to me that MLAT is a function of the distance between receivers, At 0.5uS, the distance a radio wave travels is 150 meters. Throw in some error and worst case it, you are still talking less than a km. Good enough for MLAT considering the option is no location information. The flightradar24 decoders are using a Beaglebone Black with the radar cape. That unit claims a 100MHz clock, so the timing resolution is 10ns. But my recollection is the GPSDO units only do around 100ns when the dust settles. The radarcape uses an FPGA, so it doesn't have the computer delay issue and is probably limited by the GPSDO accuracy. Personally for the cost, I'd take the 1km error from the DVB-T stick and call it a day. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
On Sat, 22 Mar 2014 06:58:22 -0700 (PDT) J. Forster j...@quikus.com wrote: I'm not so sure it is worth much as parts, except possibly on the black market. I believe the aircraft industry is big on tracking every part, cradle to grave. After all an under spec bolt can cause a very expensive crash. YMMV, -John Well timing related (just barely), scraping an airplane is a function of the metals market. For those in southern Ca., KVCV (Southern California Logistics) is where they melt down the old planes. These salvage yards knew the content of each bird down to a science, and thus know when to start the process. If you slip them $20, they will let you tour the boneyard. Same goes for Mojave. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
In message 20140323014515.0fffd232@linux-wh01, nuts writes: These salvage yards knew the content of each bird down to a science, and thus know when to start the process. We had an interesting event in Denmark related to that: Somebody hadn't heard about Mag-Thor, and tried to drive a truckload of old military scrap through the radiation detection portal at a scrap-yard :-) -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
From: nuts Note that the ADS-B mentioned is just a fancy version of the transponder that was turned off. I ran into your R Pi page about halfway in the process of doing my Beaglebone Black RTLSDR page. I have RTLSDR and dump1090 running on Angstrom Linux. I bought the GPS you suggested and will attempt to get NTP going with it, so expect a question or two off line. ;-) I wonder if your problem with the timing is related to the R Pi being nearly maxed out. The Beaglebone Black is about 4x the processing power of the R Pi, with dump1090 running at 30% CPU. Seems to me that MLAT is a function of the distance between receivers, At 0.5uS, the distance a radio wave travels is 150 meters. Throw in some error and worst case it, you are still talking less than a km. Good enough for MLAT considering the option is no location information. The flightradar24 decoders are using a Beaglebone Black with the radar cape. That unit claims a 100MHz clock, so the timing resolution is 10ns. But my recollection is the GPSDO units only do around 100ns when the dust settles. The radarcape uses an FPGA, so it doesn't have the computer delay issue and is probably limited by the GPSDO accuracy. Personally for the cost, I'd take the 1km error from the DVB-T stick and call it a day. Nuts, No problem with off-line questions - providing it's not already covered on the Web page! The Raspberry Pi is running at 35% CPU for decoding mode-S data, and 45% if you add mode-A/C data, so it doesn't appear to be maxed out - at least with the load here. Interesting that even with the extra CPU power of the BeagleBone Black you still see as high as 30% CPU. The author of the software once said that all the memory movement was the main CPU load, to which I asked whether using the DMA controllers might help, but apparently that's not easy to do, and the DMA registers are shared with other functions, IIRC. Malcolm Robb, the author, is very open to comments, though. It seems that the present software (either timing the reading the DVB-T stick or the Mlat processing) cannot produce good enough results from the DVB-T stick, something I don't quite understand. The method used is to compare the timings with aircraft of known position - as this may be off-topic there's are references here: http://www.coaa.co.uk/multilat.pdf http://planeplotter.pbworks.com/w/page/17117304/MLAT%20Introduction PlanePlotter does /not/ rely on the PC being synced to within fractions of a millisecond, as it uses relative timing with a quantisation interval determined by the receiver (50 ns for the SBS receiver, 500 ns for the DVB-T stick). The RadarCape with its GPS not only provides accurate absolute time (within 100 ns), but absolute position as well. Of course, it costs about a hundred times more than a DVB-T stick! Cheers, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
There is a newer system getting phased in: ADS-B For info MH370 did transmit ADS-B signals up to 17:21 UTC on 7 March when it seems it was either switched off or disabled. You can still see the track it took up to this time using the playback facility on Flight Radar 24 by say starting at around 17:00 UTC on 7 March. The flight No on ADS-B is slightly different and shows as MAS370 rather than MH370. Both are quoted on Flight Radar 24 when you click on the aircraft to see its track. http://www.flightradar24.com/7.69,100.35/6 Regards Rex VK7MO ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
Da: rmon...@bigpond.net.au Data: 23/03/2014 10.58 For info MH370 did transmit ADS-B signals up to 17:21 UTC on 7 March when it seems it was either switched off or disabled. You can still see the track it took up to this time using the playback facility on Flight Radar 24 by say starting at around 17:00 UTC on 7 March. The flight No on ADS-B is slightly different and shows as MAS370 rather than MH370. Both are quoted on Flight Radar 24 when you click on the aircraft to see its track. http://www.flightradar24.com/7.69,100.35/6 It seems to me that this has not yet been mentioned: Flightradar24 offers for free a Radcape ADS-B receiver (which includes a GPS receiver) provided that you have a good location and a continuous internet connection. The unit may work stand-alone and doesn't need a computer. Check if you may apply starting from here: http://www.flightradar24.com/increase-coverage Antonio I8IOV ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
On Sun, Mar 23, 2014 at 3:37 AM, nuts n...@lazygranch.com wrote: Note that the ADS-B mentioned is just a fancy version of the transponder that was turned off. I guess it depends on your concept of what a transponder does. Yes, ADS-B does transmit in the same band as the standard transponder (1090MHz) but the function and content of the transmissions are very different. With the standard mode-A, mode-C, and mode-S system, the transponder only replies to interrogation, and then only replies with the 12-bit ID code (mode-A) or 12-bit ID code plus 12-bit altitude code (mode-C). Mode-S turns it into a two-way data link and adds a bit more more data (aircraft ID) to the reply. The key here is that, if nothing is sending an interrogation, the transponder is silent. The interrogating station must do the position determination based on distance and azimuth of the reply. In the case of ADS-B, the transponder is no longer just a transponder. It is a full transceiver with an application, ADS-B, sending unsolicited data. In this case the aircraft actively transmits its position and velocity data along with its ID. No interrogation is required. Anyone within range and with a receiver can pick up the signal and determine the location of the transmitting aircraft. This means it is possible for a receiver to collect this data passively. The major problem with ADS-B is that they came up with two systems and, rather than fight it out to determine which would win, they just adopted both systems. So we have ADS-B on 978MHz using a bit more sensible modulation and framing, and on 1090MHz using the older OOK pulse-code modulation (1090ES). And to add insult to injury, they have mandated that anything that flies at FL180 (18,000') or above (meaning all airliners) must use 1090ES. The transmission mode for 1090ES (extended squitter) is very inefficient. The signal is broad as a barn door due to the use of pulse code modulation using on-off keying. Each transmission requires 5 frames. The end result is that it isn't going to take a lot of airplanes transmitting in the same airspace before you saturate the channel. So you have two separate-and-incompatible ADS-B systems flying around. The FAA solved this problem by deploying a series of ground stations that will repeat ADS-B data from one channel onto the other. If a ground station detects transmissions on 978MHz, it will repeat them on 1090MHz and repeat transmissions from 1090MHz onto 978MHz, otherwise it is silent. This means that a receiver-only system is not guaranteed to see all traffic unless one has receivers for both bands. If an aircraft is to be completely autonomous for traffic detection, the aircraft must transmit and receive on both bands. Alternatively it can transmit and receive on 978 and rely on the ground stations to repeat the 1090ES traffic. Also, because of the capacity limitations of 1090ES, the FAA does not data link weather data on 1090ES. That is only available on 978MHz. So any aircraft wishing to avail itself of the ground-based weather radar data and ground weather reporting must have a receiver for 978MHz. Bottom line, ultimately every aircraft is essentially going to need both systems. (I'm sorry but the level of stupidity that led to the ADS-B design as it now stands just boggles my mind. You have to work at it in order to take something so conceptually simple and make it this brain-damaged.) -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
FR24 got a bit picky with their latest generation receiver since so many of the first generation units walked. What they have been doing lately is giving them to flight schools, which are a bit more responsible than your average schmuck. You can monitor any of these decoders with http://www.virtualradarserver.co.uk/ To keep this timing related. there is am open source program to calibrate these DVB-T dongles based on LTE signals. http://www.serverfault.sk/2012/10/lte-cell-scanner/ I got this running on Opensuse 12.3. I haven't run it lately. Due to the bandwidth limit of the rtlsdr-, you can only scan the 700MHz LTE signals (Verizon). ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
Hi While you would *think* that LTE and PCS signals would be locked to “something good”, that’s not always the case. If you decide to use something like this for timing, it’s best to check things out carefully. Symmetricom learned this the hard way on one of their boxes …. Bob On Mar 23, 2014, at 6:28 PM, nuts n...@lazygranch.com wrote: FR24 got a bit picky with their latest generation receiver since so many of the first generation units walked. What they have been doing lately is giving them to flight schools, which are a bit more responsible than your average schmuck. You can monitor any of these decoders with http://www.virtualradarserver.co.uk/ To keep this timing related. there is am open source program to calibrate these DVB-T dongles based on LTE signals. http://www.serverfault.sk/2012/10/lte-cell-scanner/ I got this running on Opensuse 12.3. I haven't run it lately. Due to the bandwidth limit of the rtlsdr-, you can only scan the 700MHz LTE signals (Verizon). ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
jleik...@leikhim.com said: In retrospect it is kind of crazy that fleet owners will put tracking devices on $100K semi trucks and cranes yet $100 million aircraft have to rely upon 60 year old technology (Transponders) and ACARS to keep track of them. I don't question the utility of TCAS and Transponders, it is just the issue of not tracking such a valuable asset that is kind of crazy. Can you imagine how much an aircraft like that is worth in spare parts alone? -on the world market. If I were an insurer I would be asking questions of the industry. There is a newer system getting phased in: ADS-B http://en.wikipedia.org/wiki/Automatic_dependent_surveillance-broadcast The plane broadcasts it's position and velocity every second. The SDR folks are having fun with it. With one of the USB TV receiver gizmos and a Raspberry Pi, you are limited by the height of your antenna vs curvature of the earth. A friend with an antenna 20(?) feet up gets planes out to several hundred miles. I don't know how far it will work if you have an antenna on top of a hill. http://www.rtl-sdr.com/adsb-aircraft-radar-with-rtl-sdr/ Is it time to kill this topic on time-nuts? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
From: Hal Murray There is a newer system getting phased in: ADS-B http://en.wikipedia.org/wiki/Automatic_dependent_surveillance-broadcast The plane broadcasts it's position and velocity every second. The SDR folks are having fun with it. With one of the USB TV receiver gizmos and a Raspberry Pi, you are limited by the height of your antenna vs curvature of the earth. A friend with an antenna 20(?) feet up gets planes out to several hundred miles. I don't know how far it will work if you have an antenna on top of a hill. http://www.rtl-sdr.com/adsb-aircraft-radar-with-rtl-sdr/ == .. and by sharing this data on a central server you can overcome the line-of-sight limitation: http://www.satsignal.eu/raspberry-pi/dump1090.html There is a further development which may be of interest to the more mathematically oriented time-nuts, creating positions of aircraft which do no send out their position with ADS-B but use earlier responses. By comparing the timing of responses from aircraft which do send position with those that don't you can multilaterate a position for the position-less aircraft. This requires timing in the receiver device to a level of about 100 nanoseconds, most often achieved with a simple crystal oscillator (but which needs calibration). In the DVB-T sticks the usable sampling rate is about 2 MHz, and the resulting 500 microsecond resolution appears not to be good enough for even a basic multilateration fix. If anyone is interested further or could help with suggestions on improved accuracy with the DVB-T sticks, a suitable place would be the Plane Plotter Yahoo group: http://groups.yahoo.com/group/planeplotter/ Cheers, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
In message 532d1009.6040...@leikhim.com, Joe Leikhim writes: In retrospect it is kind of crazy that fleet owners will put tracking devices on $100K semi trucks and cranes yet $100 million aircraft have to rely upon 60 year old technology (Transponders) and ACARS to keep track of them. Pilots Unions and national security has a lot to do with that. Can you imagine how much an aircraft like that is worth in spare parts alone? It is worth more as scrap metal. There is no market for untraced spare parts for large passenger jets. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
On 3/21/14 8:52 PM, nuts wrote: On Thu, 20 Mar 2014 14:42:42 -0400 Joe Leikhim jleik...@leikhim.com wrote: I just red somewhere that the last ping was the only one recorded by Inmarsat system, Pings up to that point were presumed to occur due to known reporting intervals. So there is no track. T Maybe there is a market for Orbcomm asset tracking transmitters mounted way up in an inaccessible location of the tail with own back up battery supply. Tracking isn't the problem.. Argos does nice tracks of birds, fish, etc, with 10 gram transmitters, etc. It would be a trivial matter to have a GPS receiver feed into a inmarsat transmitter (like the ACARS data) and beacon every minute. But it would cost money (big money) It's more that there's no real economic need to do the tracking. All the stuff they've been flailing around with provides information that sort of, sometimes, might be able to infer some kind of position, but was never intended to do that, and certainly not in real time. Most of this stuff is intended for long term maintenance and monitoring (is the satellite in the right place.. are the engines due for service). It's only after the fact (which is an unlikely occurrence..big planes are lost something like once every 5-10 years) that people get all excited and want to do things. Someone has to foot the bill for it, and *in the long run* there's not a lot of benefit. Does the airline care how long it takes to find the wreck or plane? Not really - it's more of a PR problem than anything else, and it's hard to put a dollar value on that. In fact, once could cynically say that the airline (and aircraft mfr, and a lot of people involved) might rather the plane stay missing and never be found. If it's found, then there's evidence that will be argued about in court, and used to attempt to assign responsibility. If it's not found, after a few months, the excitement will die down, the insurance company will pay off, etc. It took months to find and recover the black box from the Air France flight ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
On Fri, Mar 21, 2014 at 11:22 PM, Joe Leikhim jleik...@leikhim.com wrote: In retrospect it is kind of crazy that fleet owners will put tracking devices on $100K semi trucks and cranes yet $100 million aircraft have to rely upon 60 year old technology (Transponders) and ACARS to keep track of them. I don't question the utility of TCAS and Transponders, it is just the issue of not tracking such a valuable asset that is kind of crazy. Can you imagine how much an aircraft like that is worth in spare parts alone? -on the world market. If I were an insurer I would be asking questions of the industry. First, just because you imagine there is a problem does not mean that there is a problem. It is possible to determine the position of every airplane but they just don't go missing all that often, as this recent event illustrates. If this were a common problem, we wouldn't be talking about it. ;-) But the solution already exists and is being deployed - ADS-B. By 2020 each aircraft will be beaconing its ID, position, and velocity vector on 978MHz and/or 1090MHz. The solution for long over-water tracking is either to receive and relay such information, or put up some LEO birds to wiretap and forward the broadcasts. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
On 22/03/14 09:01, Poul-Henning Kamp wrote: In message 532d1009.6040...@leikhim.com, Joe Leikhim writes: In retrospect it is kind of crazy that fleet owners will put tracking devices on $100K semi trucks and cranes yet $100 million aircraft have to rely upon 60 year old technology (Transponders) and ACARS to keep track of them. Pilots Unions and national security has a lot to do with that. It's a mess. Can you imagine how much an aircraft like that is worth in spare parts alone? It is worth more as scrap metal. There is no market for untraced spare parts for large passenger jets. I was about to make the same comment. The paperwork on such commercial airplanes is quite different from cars. Besides, the serial numbers would be completely traceable, removing them it turns the part into a worthless crap, so only some of them might be useful for a prop but that's about it. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
I'm not so sure it is worth much as parts, except possibly on the black market. I believe the aircraft industry is big on tracking every part, cradle to grave. After all an under spec bolt can cause a very expensive crash. YMMV, -John == In retrospect it is kind of crazy that fleet owners will put tracking devices on $100K semi trucks and cranes yet $100 million aircraft have to rely upon 60 year old technology (Transponders) and ACARS to keep track of them. I don't question the utility of TCAS and Transponders, it is just the issue of not tracking such a valuable asset that is kind of crazy. Can you imagine how much an aircraft like that is worth in spare parts alone? -on the world market. If I were an insurer I would be asking questions of the industry. Orbcomm is kind of troublesome. There is a tracking service used mostly by helicopters, which of course are notorious for falling off the radar due to low altitude. It is Iridium based. http://us.spidertracks.com/ I've used or have know users various satellite messaging services over the years. Iridium is good. I was a Globcomm customer, but it was not reliable. A friend was on Orbcomm and it had issues as well. -- Joe Leikhim Leikhim and Associates Communications Consultants Oviedo, Florida jleik...@leikhim.com 407-982-0446 WWW.LEIKHIM.COM ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
Actually traceability of parts for maintenance has nothing to do with unions and national security. It has everything to do with failure analysis. If a part fails it's entire path from manufacturer to maintanance and repair shops can be traced so if a part starts experiencing failures at Sn 12345 maintenance shops worldwide can be alerted It's why a plane with no maintenance log is essentially worthless as every track able part needs to be dismounted and inspected and a new 'yellow tag' issued or compenent scrapped if no serial found Sent from my iPhone On Mar 22, 2014, at 9:37 AM, Magnus Danielson mag...@rubidium.dyndns.org wrote: On 22/03/14 09:01, Poul-Henning Kamp wrote: In message 532d1009.6040...@leikhim.com, Joe Leikhim writes: In retrospect it is kind of crazy that fleet owners will put tracking devices on $100K semi trucks and cranes yet $100 million aircraft have to rely upon 60 year old technology (Transponders) and ACARS to keep track of them. Pilots Unions and national security has a lot to do with that. It's a mess. Can you imagine how much an aircraft like that is worth in spare parts alone? It is worth more as scrap metal. There is no market for untraced spare parts for large passenger jets. I was about to make the same comment. The paperwork on such commercial airplanes is quite different from cars. Besides, the serial numbers would be completely traceable, removing them it turns the part into a worthless crap, so only some of them might be useful for a prop but that's about it. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
Can you imagine how much an aircraft like that is worth in spare parts alone? It is worth more as scrap metal. There is no market for untraced spare parts for large passenger jets. I was just going to say the same thing. Selling parts from a stolen 777 is like being an art thieve who just stole the Mona Lisa. Yes it would be valuable but selling it to any legitimate buyer would be impossible. What airline would want parts with serial numbers traceable from a stolen aircraft? Every part on that plan has a paper trail. That said, planes (smaller planes, not airliners) do get stolen. Typically they are taken while parked at night and just flown off. They end up in the drug trade, not sold for parts. I can't think of any reason to take an airliner unless what you really want is the contents, either the cargo or the passengers. Come to think of it 100,000 iPhones at $500 each adds up to a ton of money. It might pay to be a simple pirate and simply steel the cargo no political or religious motives at all, just the valuable goods in the hold. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
On 22/03/14 21:19, Chris Albertson wrote: Can you imagine how much an aircraft like that is worth in spare parts alone? It is worth more as scrap metal. There is no market for untraced spare parts for large passenger jets. I was just going to say the same thing. Selling parts from a stolen 777 is like being an art thieve who just stole the Mona Lisa. Yes it would be valuable but selling it to any legitimate buyer would be impossible. What airline would want parts with serial numbers traceable from a stolen aircraft? Every part on that plan has a paper trail. That said, planes (smaller planes, not airliners) do get stolen. Typically they are taken while parked at night and just flown off. They end up in the drug trade, not sold for parts. I can't think of any reason to take an airliner unless what you really want is the contents, either the cargo or the passengers. Come to think of it 100,000 iPhones at $500 each adds up to a ton of money. It might pay to be a simple pirate and simply steel the cargo no political or religious motives at all, just the valuable goods in the hold. I think we deviated away from the tf aspect of the thread. Let's stop it. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
Hi Brian: MH370 had both ACARS and ADS-B, they have not been of any help. ACARS can send it's data using (in order) VHF, Inmarsat, HF. The problem is that ACARS quit sending information. MH370 did not have a contract wtih Inmarsat. ADS-B is built using W.W.II IFF technology (1090/1030 MHz, i.e. 30 MHz IF) and is called secondary radar. It's the rod looking antenna above the rotating radar antenna at airports. There are a couple of problems with it, first like VHF it's line of sight so no good over oceans and in the case of MH370 it stopped sending data. The Emergency Location Beacons (there are maybe a half dozen on most over ocean airplanes) are coupled with life rafts and only work when there are people there to turn them on (i.e. people to be rescued). These beacons typically have a GPS receiver and within minutes have transmitted not only their location but the type of vehicle, number of people on board, a contact phone number, etc. These 406 MHz beacons talk to the SARSAT system. There are two scenarios regarding MH370: 1) there was some event, like a small fire with smoke that killed all on board, or 2) someone in the cockpit (which has a door that can not be opened from the outside) wanted to commit suicide in such a way that it could not be proved that's what happened so his family would get the insurance. Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html Brian Lloyd wrote: On Fri, Mar 21, 2014 at 11:22 PM, Joe Leikhim jleik...@leikhim.com wrote: In retrospect it is kind of crazy that fleet owners will put tracking devices on $100K semi trucks and cranes yet $100 million aircraft have to rely upon 60 year old technology (Transponders) and ACARS to keep track of them. I don't question the utility of TCAS and Transponders, it is just the issue of not tracking such a valuable asset that is kind of crazy. Can you imagine how much an aircraft like that is worth in spare parts alone? -on the world market. If I were an insurer I would be asking questions of the industry. First, just because you imagine there is a problem does not mean that there is a problem. It is possible to determine the position of every airplane but they just don't go missing all that often, as this recent event illustrates. If this were a common problem, we wouldn't be talking about it. ;-) But the solution already exists and is being deployed - ADS-B. By 2020 each aircraft will be beaconing its ID, position, and velocity vector on 978MHz and/or 1090MHz. The solution for long over-water tracking is either to receive and relay such information, or put up some LEO birds to wiretap and forward the broadcasts. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
In message 532e01ee.3040...@pacific.net, Brooke Clarke writes: There are two scenarios regarding MH370: [...] Three: 3) Somebody stole the plane for some reason. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
At this time, the most likely story was written by a pilot and appeared in Wired magazine. Google MH370 smoke and look for the Wired reference. Bill Hawkins -Original Message- From: Poul-Henning Kamp Sent: Saturday, March 22, 2014 5:44 PM In message 532e01ee.3040...@pacific.net, Brooke Clarke writes: There are two scenarios regarding MH370: [...] Three: 3) Somebody stole the plane for some reason. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
On Thu, 20 Mar 2014 14:42:42 -0400 Joe Leikhim jleik...@leikhim.com wrote: I just red somewhere that the last ping was the only one recorded by Inmarsat system, Pings up to that point were presumed to occur due to known reporting intervals. So there is no track. The Inmarsat data is a red herring. The plane could have ditched into the water 85 minutes after the incident:, at location near last radar contact and floated with Inmarsat operating on service battery for hours. The ELT's used in this aircraft have been implicated in two fires due to shorted lithium battery wires. There was an AD/Recall issued. No reports whatsoever about the ELT being activated, so if it burned.. Good only for 48 hours or so anyway if looking in the wrong place. Maybe there is a market for Orbcomm asset tracking transmitters mounted way up in an inaccessible location of the tail with own back up battery supply. Orbcomm is kind of troublesome. There is a tracking service used mostly by helicopters, which of course are notorious for falling off the radar due to low altitude. It is Iridium based. http://us.spidertracks.com/ I've used or have know users various satellite messaging services over the years. Iridium is good. I was a Globcomm customer, but it was not reliable. A friend was on Orbcomm and it had issues as well. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
In retrospect it is kind of crazy that fleet owners will put tracking devices on $100K semi trucks and cranes yet $100 million aircraft have to rely upon 60 year old technology (Transponders) and ACARS to keep track of them. I don't question the utility of TCAS and Transponders, it is just the issue of not tracking such a valuable asset that is kind of crazy. Can you imagine how much an aircraft like that is worth in spare parts alone? -on the world market. If I were an insurer I would be asking questions of the industry. Orbcomm is kind of troublesome. There is a tracking service used mostly by helicopters, which of course are notorious for falling off the radar due to low altitude. It is Iridium based. http://us.spidertracks.com/ I've used or have know users various satellite messaging services over the years. Iridium is good. I was a Globcomm customer, but it was not reliable. A friend was on Orbcomm and it had issues as well. -- Joe Leikhim Leikhim and Associates Communications Consultants Oviedo, Florida jleik...@leikhim.com 407-982-0446 WWW.LEIKHIM.COM ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
On Wed, Mar 19, 2014 at 09:28:38PM -0700, nuts wrote: A lot of these satellites have footprints for each antenna. I don't know if the footprints are narrow enough to track a plane. I do believe there is an time offset for each aircraft sent on the forward control channel from the ground (which is shared with many aircraft) that allows a particular aircraft to transmit a frame in the center of its allocated slot. IIRC the ground measures the error and sends a correction to the plane which allows the plane's transceiver to compute just when - relative to the system frame timing derived from the received forward control channel from the satellite - it should transmit the reverse control channel burst. -- Dave Emery N1PRE/AE, d...@dieconsulting.com DIE Consulting, Weston, Mass 02493 An empty zombie mind with a forlorn barely readable weatherbeaten 'For Rent' sign still vainly flapping outside on the weed encrusted pole - in celebration of what could have been, but wasn't and is not to be now either. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
In message 279331507.5734621395275538874.JavaMail.actor@webmail5, iovane@inw ind.it writes: My question was on what would be the expected accuracy of the circle's radius. Projected onto the surface of the earth, the uncertainty leaves a band approx 740km wide. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
On 3/20/14 12:07 AM, Poul-Henning Kamp wrote: In message 279331507.5734621395275538874.JavaMail.actor@webmail5, iovane@inw ind.it writes: My question was on what would be the expected accuracy of the circle's radius. Projected onto the surface of the earth, the uncertainty leaves a band approx 740km wide. Is there a document that describes the system somewhere? I've seen various descriptions of what's going on. Do they use timing or amplitude measurements? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
Would think they have many other aircraft with known position stationary or moving with location known to help improve the estimate. Stanley - Original Message - From: Jim Lux jim...@earthlink.net To: time-nuts@febo.com Sent: Thursday, March 20, 2014 8:05 AM Subject: Re: [time-nuts] Aircraft ping timing On 3/20/14 12:07 AM, Poul-Henning Kamp wrote: In message 279331507.5734621395275538874.JavaMail.actor@webmail5, iovane@inw ind.it writes: My question was on what would be the expected accuracy of the circle's radius. Projected onto the surface of the earth, the uncertainty leaves a band approx 740km wide. Is there a document that describes the system somewhere? I've seen various descriptions of what's going on. Do they use timing or amplitude measurements? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
In message 40280C39FE7D43C79313A1755BCAF58D@StanleyPC, Stanley writes: Would think they have many other aircraft with known position stationary or moving with location known to help improve the estimate. They might have been able to do that while the plane responded, but now that the plane is silent it is too late. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
In message 532ae780.4020...@earthlink.net, Jim Lux writes: On 3/20/14 12:07 AM, Poul-Henning Kamp wrote: Is there a document that describes the system somewhere? I've seen various descriptions of what's going on. Do they use timing or amplitude measurements? It is a timing measurement and it's not really designed to be precise. I belive the basic timing accuracy just below +/- 1msec. As the signal flies, that is +/- 300km. Projecting that onto the spherical planet, with an antenna angle around 40 degrees smears it out by a factor of roughly 1.5 and that's where the 740 km comes from. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
On 3/20/14 8:53 AM, Poul-Henning Kamp wrote: In message 40280C39FE7D43C79313A1755BCAF58D@StanleyPC, Stanley writes: Would think they have many other aircraft with known position stationary or moving with location known to help improve the estimate. They might have been able to do that while the plane responded, but now that the plane is silent it is too late. It's also not something they really do as part of regular operations. It's probably more like a long term performance monitoring thing to make sure the satellite isn't degrading, or mis pointed. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
Missing plane this ping was not lost why would others be lost ? This ping was retrieved long after (days) it was received why would it be the only one ? Stanley - Original Message - From: Jim Lux jim...@earthlink.net To: time-nuts@febo.com Sent: Thursday, March 20, 2014 11:05 AM Subject: Re: [time-nuts] Aircraft ping timing On 3/20/14 8:53 AM, Poul-Henning Kamp wrote: In message 40280C39FE7D43C79313A1755BCAF58D@StanleyPC, Stanley writes: Would think they have many other aircraft with known position stationary or moving with location known to help improve the estimate. They might have been able to do that while the plane responded, but now that the plane is silent it is too late. It's also not something they really do as part of regular operations. It's probably more like a long term performance monitoring thing to make sure the satellite isn't degrading, or mis pointed. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
In message B55E2883CD3E43878AE5CB77C259E572@StanleyPC, Stanley writes: Missing plane this ping was not lost why would others be lost ? This ping was retrieved long after (days) it was received why would it be the only one ? The point is that they might have been able to do more precise pings in real-time, but now that it's on file in lower resolution, that's too late. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
I just red somewhere that the last ping was the only one recorded by Inmarsat system, Pings up to that point were presumed to occur due to known reporting intervals. So there is no track. The Inmarsat data is a red herring. The plane could have ditched into the water 85 minutes after the incident:, at location near last radar contact and floated with Inmarsat operating on service battery for hours. The ELT's used in this aircraft have been implicated in two fires due to shorted lithium battery wires. There was an AD/Recall issued. No reports whatsoever about the ELT being activated, so if it burned.. Good only for 48 hours or so anyway if looking in the wrong place. Maybe there is a market for Orbcomm asset tracking transmitters mounted way up in an inaccessible location of the tail with own back up battery supply. -- Joe Leikhim Leikhim and Associates Communications Consultants Oviedo, Florida jleik...@leikhim.com 407-982-0446 WWW.LEIKHIM.COM ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
They only got one ping from INMARSAT at 64E above the Indian Ocean. There was no other ping to triangulate the position. One ping projects a circle on the Earth. The maximum flying range of the plane determined the ends of the NE and SE arcs of that circle. The news only gets stranger as time goes on. Bill Hawkins -Original Message- From: iov...@inwind.it Sent: Wednesday, March 19, 2014 6:46 PM Those who say the missing aircraft should be searched along the two corridors, what measurement are they relying on? I think it is a one-way measurement of time-stamped pings, which implies good synchronization of clocks between a geosynchronous satellite and a moving aircraft. Antonio I8IOV ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
My question was on what would be the expected accuracy of the circle's radius. Antonio I8IOV Messaggio originale Da: b...@iaxs.net Data: 20/03/2014 1.21 They only got one ping from INMARSAT at 64E above the Indian Ocean. There was no other ping to triangulate the position. One ping projects a circle on the Earth. The maximum flying range of the plane determined the ends of the NE and SE arcs of that circle. The news only gets stranger as time goes on. Bill Hawkins -Original Message- From: iov...@inwind.it Sent: Wednesday, March 19, 2014 6:46 PM Those who say the missing aircraft should be searched along the two corridors, what measurement are they relying on? I think it is a one-way measurement of time-stamped pings, which implies good synchronization of clocks between a geosynchronous satellite and a moving aircraft. Antonio I8IOV ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
It depends on how accurately the bird can measure the round-trip time: 1 us = ca 500' 10 us = ca 1 mile 100us = ca 10 miles 1 ms = ca 100 miles The arcs are loci of constant round trip time, projected on the globe. -John === My question was on what would be the expected accuracy of the circle's radius. Antonio I8IOV Messaggio originale Da: b...@iaxs.net Data: 20/03/2014 1.21 They only got one ping from INMARSAT at 64E above the Indian Ocean. There was no other ping to triangulate the position. One ping projects a circle on the Earth. The maximum flying range of the plane determined the ends of the NE and SE arcs of that circle. The news only gets stranger as time goes on. Bill Hawkins -Original Message- From: iov...@inwind.it Sent: Wednesday, March 19, 2014 6:46 PM Those who say the missing aircraft should be searched along the two corridors, what measurement are they relying on? I think it is a one-way measurement of time-stamped pings, which implies good synchronization of clocks between a geosynchronous satellite and a moving aircraft. Antonio I8IOV ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
Messaggio originale Da: j...@quikus.com Data: 20/03/2014 1.47 It depends on how accurately the bird can measure the round-trip time: 1 us = ca 500' 10 us = ca 1 mile 100us = ca 10 miles 1 ms = ca 100 miles The arcs are loci of constant round trip time, projected on the globe. This is valid for round trip and for the signal path which in this case is the line generating the cone having the bird at its apex. The radius of the circle at earth is another thing, and the error should be multiplied by some factor which depends on the angle at the apex, being the earth's surface curve. Hence I tought that the timing is crucial. Add to this that I understood it was not a ping as we usually mean, but a one way signal (aircraft to satellite). Hence my question. Antonio I8IOV -John === My question was on what would be the expected accuracy of the circle's radius. Antonio I8IOV Messaggio originale Da: b...@iaxs.net Data: 20/03/2014 1.21 They only got one ping from INMARSAT at 64E above the Indian Ocean. There was no other ping to triangulate the position. One ping projects a circle on the Earth. The maximum flying range of the plane determined the ends of the NE and SE arcs of that circle. The news only gets stranger as time goes on. Bill Hawkins -Original Message- From: iov...@inwind.it Sent: Wednesday, March 19, 2014 6:46 PM Those who say the missing aircraft should be searched along the two corridors, what measurement are they relying on? I think it is a one-way measurement of time-stamped pings, which implies good synchronization of clocks between a geosynchronous satellite and a moving aircraft. Antonio I8IOV ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
Hi Antonio: It's my understanding that the satellite sends a ping to each aircraft in it's low gain antenna pattern once every hour by aircraft ID number. The aircraft replies with a very short data packet that's time stamped (but without any location or other info other than the ID). The difference between the time stamp on the ping and the received message is the ping time. The idea is to have some idea which of the spot beams to use if someone on the plane wanted to make a phone call. As it happens MH370 does not have first class or sat phones, but this is the default system for everyone. Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html iov...@inwind.it wrote: Messaggio originale Da: j...@quikus.com Data: 20/03/2014 1.47 It depends on how accurately the bird can measure the round-trip time: 1 us = ca 500' 10 us = ca 1 mile 100us = ca 10 miles 1 ms = ca 100 miles The arcs are loci of constant round trip time, projected on the globe. This is valid for round trip and for the signal path which in this case is the line generating the cone having the bird at its apex. The radius of the circle at earth is another thing, and the error should be multiplied by some factor which depends on the angle at the apex, being the earth's surface curve. Hence I tought that the timing is crucial. Add to this that I understood it was not a ping as we usually mean, but a one way signal (aircraft to satellite). Hence my question. Antonio I8IOV -John === My question was on what would be the expected accuracy of the circle's radius. Antonio I8IOV Messaggio originale Da: b...@iaxs.net Data: 20/03/2014 1.21 They only got one ping from INMARSAT at 64E above the Indian Ocean. There was no other ping to triangulate the position. One ping projects a circle on the Earth. The maximum flying range of the plane determined the ends of the NE and SE arcs of that circle. The news only gets stranger as time goes on. Bill Hawkins -Original Message- From: iov...@inwind.it Sent: Wednesday, March 19, 2014 6:46 PM Those who say the missing aircraft should be searched along the two corridors, what measurement are they relying on? I think it is a one-way measurement of time-stamped pings, which implies good synchronization of clocks between a geosynchronous satellite and a moving aircraft. Antonio I8IOV ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
On 3/19/14 5:21 PM, Bill Hawkins wrote: They only got one ping from INMARSAT at 64E above the Indian Ocean. There was no other ping to triangulate the position. One ping projects a circle on the Earth. The maximum flying range of the plane determined the ends of the NE and SE arcs of that circle. The news only gets stranger as time goes on. not time based...from what I understand it's based on a received power estimate, matched against antenna patterns. Not particularly accurate. The power measurement is probably good to 0.2 dB (at best). If the transmit antenna's attitude isn't in the nominal straight and level (e.g. plane is banking, or parked on ground, perhaps with a tarp placed by a overweight gentleman holding a white furry cat on his lab?) I did some back of the envelopes and there's a good many 100s of km uncertainty in range. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Aircraft ping timing
A lot of these satellites have footprints for each antenna. I don't know if the footprints are narrow enough to track a plane. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
