Re: [time-nuts] sub-minute time-precision in court-case
On 09/04/2013 01:59 AM, Jim Lux wrote: On 9/3/13 11:21 AM, Poul-Henning Kamp wrote: In message 5225f8af.60...@earthlink.net, Jim Lux writes: In this case, all the messages were presumably handled by the same carrier, so the issue of skew in timestamps is negligible; Anything but. The text-messages are likely stamped by the SS7-message-gateway and the 911 call by the countys 911 equipment. I was assuming (with no real basis, I realize) that the 911 call time came from the cell equipment, rather than the Public Safety Answering Point log. The PSAP log would have no particular reason to be synced to the carrier equipment. It could well be what time was on the watch of the guy starting the equipment, although these days, one would *think* that they use something like NTP to set the system time. However, given my frustrated experience trying to get folks doing testbeds and ground support equipment here at JPL to *please* synchronize your computers meaningfully so we can merge logs, I wouldn't count on it. Or maybe they sync once every 24 hours. That would be luxury! There are so many systems out there ticking away at their free-running clocks, and that does not even have the capability of an external time source. 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] sub-minute time-precision in court-case
In message 727DE1FE9A784A598E49129B80D2C63C@pc52, Tom Van Baak writes: filename=5071A-xyz.jpg As far as I can see, two of the tubes have their axis parallel to the X-coordinate ? -- 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] sub-minute time-precision in court-case
In message 522735c1.6020...@earthlink.net, Jim Lux writes: And in California, cannot be operated by those under 18, even with the hands free capability. Not to mention the fact that you can go to jail if you remove the fire-warninglabel from the foam-cushion it came packed in :-) -- 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] sub-minute time-precision in court-case
I noticed that my old Nokia phones kept time better than computers, then I learned that the oscillator in the phone is adjusted to match the BTS carrier [1]. To verify this I ran ntpd in an Android phone synced to a stratum 1 server via USB tethering. (USB has a lower latency and jitter than WLAN.) The frequency offset was between 25 ppb and 50 ppb (loopstats graph attached). When the phone is put in airplane mode, the frequency offset jumped to 11 ppm. Unfortunately Android's timekeeping gets messed up when the phone suspends since the time is restored from a possibly low resolution RTC when waking up [2, sec. 3]. The phone is prevented from suspending when connected to a USB port, another reason for using USB tethering during the test. [1] http://gnuradio.org/redmine/projects/gnuradio/wiki/OpenBTSClocks [2] https://lwn.net/images/pdf/suspend_blockers.pdf On Wed, Sep 4, 2013 at 7:58 AM, Bill Hawkins b...@iaxs.net wrote: Who among you has volunteered to do the research for this? I don't have a camera in my cell phone, and I avoid market research masquerading as insecure social networks. Bill Hawkins -Original Message- Tom Van Baak said, For extra credit, further photos can be sent each hour for hours or days to determine the cell phone frequency drift and stability parameters. ___ 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. attachment: _abs_frequency.png___ 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] sub-minute time-precision in court-case
It is very rare to see courts deal with time precisions less than minutes, but it seems to have happened in this case: (from: www.judiciary.state.nj.us/opinions/a1128-12.pdf) Best stopped his truck, saw the severity of the injuries, and called 911. The time of the 911 call was 17:49:15, that is, fifteen seconds after 5:49 p.m. [...] texts [...] exchanged while Best was driving: Sent Sender Received Recipient [...] 5:47:49 Best5:47:56 Colonna 5:48:14 Colonna 5:48:23 Best 5:48:58 Best5:49:07 Colonna (5:49:15 911 Call) This sequence indicates the precise time of the accident - within seconds of 5:48:58. Seventeen seconds elapsed from Best's sending a text to Colonna and the time of the 911 call after the accident. Those seconds had to include Best's stopping his vehicle, observing the injuries to the Kuberts, and dialing 911. It appears, therefore, that Best collided with the Kuberts' motorcycle immediately after sending a text at 5:48:58. Nowhere does the opinion mention if the timestamps were taken on the same clock or if the two clocks were synchronized. Best was a volunteer fireman, but I still find the seventeen seconds slightly incredible. The seventeen seconds are somewhat material to the ruling, but not a decisive factor. -- 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] sub-minute time-precision in court-case
On 9/3/13 7:07 AM, Poul-Henning Kamp wrote: It is very rare to see courts deal with time precisions less than minutes, but it seems to have happened in this case: Interesting (and of course, this case has been in the news recently).. In this case, all the messages were presumably handled by the same carrier, so the issue of skew in timestamps is negligible; they're all presumably running off the same clock. I wonder, though, whether this is always the case. Yes, the cell companies have accurate timing at the cell site level to do a variety of things, but I could see that getting lost along the way to the meta data logging process. The time stamp might be when the message arrived at the logging process. And, different companies might have different standards for how those timestamps get applied and their accuracy requirements. I can see how a company might have a legacy billing system that, say, works in 0.1 minute chunks, so a 6 second random scatter is inherent in the system. Given that cell companies know the location of the radio with at least a few tens of meters, it would be interesting to see statistics of text messages sent/received while on freeways. Indeed, one does not know that the person with the phone in question is a driver or passenger, but simple observation (at least in Los Angeles) shows that the vast majority of cars are single passenger (alas, even in carpool lanes, there's a significant number of them). I do know they calculate this sort of thing, because they use it to determine where to put new cell sites or change capacity. The question is whether the information is available in any sort of useful form. It could be some horribly ad hoc process where an engineer gets a bunch of text files, and they load it into Excel spreadsheets to process it. It's not like they necessarily do site planning on a minute by minute basis, so a manual process that takes a few days is plausible. (from: www.judiciary.state.nj.us/opinions/a1128-12.pdf) Best stopped his truck, saw the severity of the injuries, and called 911. The time of the 911 call was 17:49:15, that is, fifteen seconds after 5:49 p.m. [...] texts [...] exchanged while Best was driving: Sent Sender Received Recipient [...] 5:47:49 Best5:47:56 Colonna 5:48:14 Colonna 5:48:23 Best 5:48:58 Best5:49:07 Colonna (5:49:15 911 Call) This sequence indicates the precise time of the accident - within seconds of 5:48:58. Seventeen seconds elapsed from Best's sending a text to Colonna and the time of the 911 call after the accident. Those seconds had to include Best's stopping his vehicle, observing the injuries to the Kuberts, and dialing 911. It appears, therefore, that Best collided with the Kuberts' motorcycle immediately after sending a text at 5:48:58. Nowhere does the opinion mention if the timestamps were taken on the same clock or if the two clocks were synchronized. Best was a volunteer fireman, but I still find the seventeen seconds slightly incredible. Based on the behavior my cell phone (sending texts in signal denied areas), I assume the time stamp is actually the time when message processed by cell site, which could be many seconds (minutes, hours) after pushing the send button. I've had text messages queued in my phone that get sent when I land and turn my phone back on. More than once my wife has gotten the they're closing the door text from me when I landed. Well, Best did take 35 seconds to respond to the text from Colonna. I think we can assume that the incident occurred slightly after x:58 (although I suppose the sequence could have been keypress keypress keypress sound of impact keypress send message Zipping along at 30 mi/hr (14 m/s), 10 seconds is quite a distance. This was about a half an hour before sunset on that date. There was a turn in the road involved, etc. What didn't show up in the record is the lat/lon estimate for Best's cell phone. I would assume that in 2009 they were logging this as well, but maybe the data was not in evidence (the lawyers may not have wanted it.. that's the frustrating thing about reading appellate cases: you have to work with the data as presented at the original trial) The seventeen seconds are somewhat material to the ruling, but not a decisive factor. I think it's more the back and forth of messages just before the incident that are at issue: they imply that there was a conversation of sorts going on, and that the young lady may have had knowledge that he was driving at the time (which ultimately is what this case is all about). I'll bet the marketeers at the cell company have all sorts of models of texting behavior among people, just waiting for the ability to insert ads of the
Re: [time-nuts] sub-minute time-precision in court-case
On 9/3/2013 10:56 AM, Jim Lux wrote: In this case, all the messages were presumably handled by the same carrier, so the issue of skew in timestamps is negligible; they're all presumably running off the same clock. But not necessarily the same time. For instance, some cell systems run on GPS time, but the carrier may keep records in UTC, since it's the legal time in most jurisdictions. A phone might time stamp using either (Google has a years-old bug in Android which lets it use GPS time and not UTC). So, different devices on the same network may not be in sync. ___ 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] sub-minute time-precision in court-case
I remember a lecture by an officer of the (London) Met Police about how tracable time was essential to demolishing the defence of wrong clock in accidents involving the illegal use of mobile phones when moving and even parking meter tickets. They had to argue why the cell time was more right than the defendants watch!! This was part of a meeting of the Time and Frequency Club at the NPL at Teddington about 6 years ago. Alan G3NYK .. - Original Message - From: Mike S mi...@flatsurface.com To: time-nuts@febo.com Sent: Tuesday, September 03, 2013 5:19 PM Subject: Re: [time-nuts] sub-minute time-precision in court-case On 9/3/2013 10:56 AM, Jim Lux wrote: In this case, all the messages were presumably handled by the same carrier, so the issue of skew in timestamps is negligible; they're all presumably running off the same clock. But not necessarily the same time. For instance, some cell systems run on GPS time, but the carrier may keep records in UTC, since it's the legal time in most jurisdictions. A phone might time stamp using either (Google has a years-old bug in Android which lets it use GPS time and not UTC). So, different devices on the same network may not be in sync. ___ 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] sub-minute time-precision in court-case
In message 5225f8af.60...@earthlink.net, Jim Lux writes: In this case, all the messages were presumably handled by the same carrier, so the issue of skew in timestamps is negligible; Anything but. The text-messages are likely stamped by the SS7-message-gateway and the 911 call by the countys 911 equipment. And yes, there can be quite a delay from you press send until the SS7-message-gateway sees the text-message. -- 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] sub-minute time-precision in court-case
You can find (for better or worse) NTSB analysis of various recorder timestamps relative to cell phone timestamp. http://www.ntsb.gov/investigations/summary/RAR1001.html 6 In this report, all times associated with the sending or receiving of calls and text messages are from Verizon records. In these records, the “sent” and “received” times are based on a GPS time reference and reflect the time the Verizon Wireless network equipment either receives or delivers a message. Thus, the reported “sent” time of a message does not necessarily correlate to the time the sender pressed the “send” button on the wireless device. Because the network must query the receiving device to make sure it is available before transmitting a message, the “received” time is more likely to reflect the actual time the message arrives on the recipient’s device. 7 In this report, all times associated with signal, switch, and locomotive events are based on signal log and locomotive event recorder data synchronized to a GPS reference time. This synchronization correlates train position, data recorder, signal, and cell phone send/receive times to a common “master clock” that reflects actual GPS time. On Tue, Sep 3, 2013 at 1:48 PM, Alan Melia alan.me...@btinternet.comwrote: I remember a lecture by an officer of the (London) Met Police about how tracable time was essential to demolishing the defence of wrong clock in accidents involving the illegal use of mobile phones when moving and even parking meter tickets. They had to argue why the cell time was more right than the defendants watch!! This was part of a meeting of the Time and Frequency Club at the NPL at Teddington about 6 years ago. Alan G3NYK .. - Original Message - From: Mike S mi...@flatsurface.com To: time-nuts@febo.com Sent: Tuesday, September 03, 2013 5:19 PM Subject: Re: [time-nuts] sub-minute time-precision in court-case On 9/3/2013 10:56 AM, Jim Lux wrote: In this case, all the messages were presumably handled by the same carrier, so the issue of skew in timestamps is negligible; they're all presumably running off the same clock. But not necessarily the same time. For instance, some cell systems run on GPS time, but the carrier may keep records in UTC, since it's the legal time in most jurisdictions. A phone might time stamp using either (Google has a years-old bug in Android which lets it use GPS time and not UTC). So, different devices on the same network may not be in sync. __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://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-nutshttps://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] sub-minute time-precision in court-case
Nowhere does the opinion mention if the timestamps were taken on the same clock or if the two clocks were synchronized. PHK, Correct. This is an age-old problem, whether its minutes or nanoseconds. Time-stamps are inherently relative to a local oscillator's time and rate offset, and affected by frequency drift and stability levels. A solution to this problem is for the first responder to take the cell phone(s) and simultaneously send a text message to himself from each phone. That could help establish a legal time difference (unless, there are variable reception or carrier-specific delays). They could also simultaneously send cell phone photos of a handheld GPS receiver's time display. That could help establish a legal time accuracy question (unless, the cell phone or GPS receiver were in some sort of hold-over mode). For extra credit, further photos can be sent each hour for hours or days to determine the cell phone frequency drift and stability parameters. Then again, realize that a jury of your fellow citizens, not a jury of your peers, will decide the question of timing. Thus to raise technical issues like syntonization vs. synchronization, or standard vs. Allan deviation, or GPS vs. UTC clocks will probably not help your case. /tvb ___ 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] sub-minute time-precision in court-case
On 09/03/2013 11:47 PM, Tom Van Baak wrote: Nowhere does the opinion mention if the timestamps were taken on the same clock or if the two clocks were synchronized. PHK, Correct. This is an age-old problem, whether its minutes or nanoseconds. Time-stamps are inherently relative to a local oscillator's time and rate offset, and affected by frequency drift and stability levels. A solution to this problem is for the first responder to take the cell phone(s) and simultaneously send a text message to himself from each phone. That could help establish a legal time difference (unless, there are variable reception or carrier-specific delays). They could also simultaneously send cell phone photos of a handheld GPS receiver's time display. That could help establish a legal time accuracy question (unless, the cell phone or GPS receiver were in some sort of hold-over mode). For extra credit, further photos can be sent each hour for hours or days to determine the cell phone frequency drift and stability parameters. Then again, realize that a jury of your fellow citizens, not a jury of your peers, will decide the question of timing. Thus to raise technical issues like syntonization vs. synchronization, or standard vs. Allan deviation, or GPS vs. UTC clocks will probably not help your case. Who is this Allan whos deviation is this or that value? Yeah, the question is even if you have a legal support for what correct time or even traceable time actually is or means. I know countries that does not even legally accept UTC. It could be better, way better. 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] sub-minute time-precision in court-case
On 09/04/2013 12:19 AM, Tom Van Baak wrote: Yeah, the question is even if you have a legal support for what correct time or even traceable time actually is or means. I know countries that does not even legally accept UTC. It could be better, way better. Cheers, Magnus Still, imagine Magnus collides with Tom. What time did it really happen? Does it help if we both have GPS? Both have cesium(s) in the back seat? At some point the notion of uncertainty and error bars needs to be allowed. We both agree, but now it is about convincing a jury... or lawyers. 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] sub-minute time-precision in court-case
Tom, Did you ever reset that thing to the correct time? =) Bob From: Tom Van Baak t...@leapsecond.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tuesday, September 3, 2013 5:19 PM Subject: Re: [time-nuts] sub-minute time-precision in court-case Yeah, the question is even if you have a legal support for what correct time or even traceable time actually is or means. I know countries that does not even legally accept UTC. It could be better, way better. Cheers, Magnus Still, imagine Magnus collides with Tom. What time did it really happen? Does it help if we both have GPS? Both have cesium(s) in the back seat? At some point the notion of uncertainty and error bars needs to be allowed. /tvb ___ 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] sub-minute time-precision in court-case
Who among you has volunteered to do the research for this? I don't have a camera in my cell phone, and I avoid market research masquerading as insecure social networks. Bill Hawkins -Original Message- Tom Van Baak said, For extra credit, further photos can be sent each hour for hours or days to determine the cell phone frequency drift and stability parameters. ___ 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] sub-minute time-precision in court-case
On 9/3/13 11:21 AM, Poul-Henning Kamp wrote: In message 5225f8af.60...@earthlink.net, Jim Lux writes: In this case, all the messages were presumably handled by the same carrier, so the issue of skew in timestamps is negligible; Anything but. The text-messages are likely stamped by the SS7-message-gateway and the 911 call by the countys 911 equipment. I was assuming (with no real basis, I realize) that the 911 call time came from the cell equipment, rather than the Public Safety Answering Point log. The PSAP log would have no particular reason to be synced to the carrier equipment. It could well be what time was on the watch of the guy starting the equipment, although these days, one would *think* that they use something like NTP to set the system time. However, given my frustrated experience trying to get folks doing testbeds and ground support equipment here at JPL to *please* synchronize your computers meaningfully so we can merge logs, I wouldn't count on it. Or maybe they sync once every 24 hours. And yes, there can be quite a delay from you press send until the SS7-message-gateway sees the text-message. ___ 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] sub-minute time-precision in court-case
On 9/3/13 2:47 PM, Tom Van Baak wrote: Nowhere does the opinion mention if the timestamps were taken on the same clock or if the two clocks were synchronized. PHK, Correct. This is an age-old problem, whether its minutes or nanoseconds. Time-stamps are inherently relative to a local oscillator's time and rate offset, and affected by frequency drift and stability levels. A solution to this problem is for the first responder to take the cell phone(s) and simultaneously send a text message to himself from each phone. That could help establish a legal time difference (unless, there are variable reception or carrier-specific delays). No way is the FR going to do anything with that phone other than drop it into a shielded bag, maybe after removing the battery. Operating the keys on the phone would be tampering with the evidence. They could also simultaneously send cell phone photos of a handheld GPS receiver's time display. That could help establish a legal time accuracy question (unless, the cell phone or GPS receiver were in some sort of hold-over mode). If that's the case, it would be done in a forensic lab with the phone hooked up to one of those fancy phone analysis systems. For extra credit, further photos can be sent each hour for hours or days to determine the cell phone frequency drift and stability parameters. Then again, realize that a jury of your fellow citizens, not a jury of your peers, will decide the question of timing. Thus to raise technical issues like syntonization vs. synchronization, or standard vs. Allan deviation, or GPS vs. UTC clocks will probably not help your case. There's a whole literature of mystery novels based on timetables and such, including clever use of that new fangled device the telephone to make someone think they are in one place rather than another. WHen *I* commit that perfect murder, and am unhappily arrested, I'm going to demand that only time-nuts sit on the jury. You've been warned. The Ventura county courthouse is in a fairly pleasant location near the shore and has a decent cafeteria. Pray I do not get arrested in Los Angeles county, which is a hellhole in which to serve as a jury member. Realistically, though, there's a lot of potential time related litigation in the securities industry. Accusations of front running in the high frequency trading area, for instance, might revolve around milliseconds. For all we know, there are litigation consultants reviewing the archives of this list at this very moment, identifying people who they would or would not want sitting on the jury. ___ 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] sub-minute time-precision in court-case
Re: time-nuts Digest, Vol 110, Issue 13 On Tue, 03 Sep 2013 19:52:17 -0400, time-nuts-requ...@febo.com wrote: Date: Wed, 04 Sep 2013 00:27:18 +0200 From: Magnus Danielson mag...@rubidium.dyndns.org To: time-nuts@febo.com Subject: Re: [time-nuts] sub-minute time-precision in court-case Message-ID: 52266246.2020...@rubidium.dyndns.org Content-Type: text/plain; charset=ISO-8859-1 On 09/04/2013 12:19 AM, Tom Van Baak wrote: Yeah, the question is even if you have a legal support for what correct time or even traceable time actually is or means. I know countries that does not even legally accept UTC. It could be better, way better. Cheers, Magnus Still, imagine Magnus collides with Tom. What time did it really happen? Does it help if we both have GPS? Both have cesium(s) in the back seat? At some point the notion of uncertainty and error bars needs to be allowed. We both agree, but now it is about convincing a jury... or lawyers. I can see it now - the focus will be on all that cesium spewed about, like with Fukushima. You'll never convince them that you are not radioactive. Joe Gwinn ___ 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] sub-minute time-precision in court-case
Re the PSAP timekeeping Requirement: See NENA 04-002, Traceable UTC Source, Master Clock Specification http://www.nena.org/resource/collection/6EE32917-37BD-4FA0-838C-026931F702A6/NENA_04-002-v4_PSAP_Master_Clock.pdf On 9/3/2013 7:59 PM, Jim Lux wrote: I was assuming (with no real basis, I realize) that the 911 call time came from the cell equipment, rather than the Public Safety Answering Point log. The PSAP log would have no particular reason to be synced to the carrier equipment. It could well be what time was on the watch of the guy starting the equipment, although these days, one would *think* that they use something like NTP to set the system time. ___ 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] sub-minute time-precision in court-case
This precisely why I stopped wearing a watch years ago Stranger: What time is it? Me: When? Stranger: What 'when'? - now of course! Me: Now - where? - Now you? or Now me? (Hint ~ 3 nsec dt) and so forth and so on. better a watch don't have - no questions On Tue, Sep 3, 2013 at 4:47 PM, Tom Van Baak t...@leapsecond.com wrote: Nowhere does the opinion mention if the timestamps were taken on the same clock or if the two clocks were synchronized. PHK, Correct. This is an age-old problem, whether its minutes or nanoseconds. Time-stamps are inherently relative to a local oscillator's time and rate offset, and affected by frequency drift and stability levels. A solution to this problem is for the first responder to take the cell phone(s) and simultaneously send a text message to himself from each phone. That could help establish a legal time difference (unless, there are variable reception or carrier-specific delays). They could also simultaneously send cell phone photos of a handheld GPS receiver's time display. That could help establish a legal time accuracy question (unless, the cell phone or GPS receiver were in some sort of hold-over mode). For extra credit, further photos can be sent each hour for hours or days to determine the cell phone frequency drift and stability parameters. Then again, realize that a jury of your fellow citizens, not a jury of your peers, will decide the question of timing. Thus to raise technical issues like syntonization vs. synchronization, or standard vs. Allan deviation, or GPS vs. UTC clocks will probably not help your case. /tvb ___ 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] sub-minute time-precision in court-case
- Original Message - From: Jim Lux jim...@earthlink.net To: Poul-Henning Kamp p...@phk.freebsd.dk Cc: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tuesday, September 03, 2013 7:59 PM Subject: Re: [time-nuts] sub-minute time-precision in court-case On 9/3/13 11:21 AM, Poul-Henning Kamp wrote: In message 5225f8af.60...@earthlink.net, Jim Lux writes: In this case, all the messages were presumably handled by the same carrier, so the issue of skew in timestamps is negligible; Anything but. The text-messages are likely stamped by the SS7-message-gateway and the 911 call by the countys 911 equipment. I was assuming (with no real basis, I realize) that the 911 call time came from the cell equipment, rather than the Public Safety Answering Point log. The PSAP log would have no particular reason to be synced to the carrier equipment. It could well be what time was on the watch of the guy starting the equipment, although these days, one would *think* that they use something like NTP to set the system time. However, given my frustrated experience trying to get folks doing testbeds and ground support equipment here at JPL to *please* synchronize your computers meaningfully so we can merge logs, I wouldn't count on it. Or maybe they sync once every 24 hours. In Maryland, all the 911 PSAPs have GPS clocks and everything (clocks, consoles, computers, logging recorders, etc.) is locked to GPS time. As far as I know, that is the NENA national standard in the US. Regards, Tom ___ 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] sub-minute time-precision in court-case
On Wed, Sep 4, 2013 at 6:19 AM, Tom Van Baak t...@leapsecond.com wrote: Does it help if we both have GPS? Both have cesium(s) in the back seat? Since the GPS communicates over Radio Frequencies, please ensure it is capable of hands-free operation while you are operating the vehicle. Next, Lady Heather has to be modified to allow voice operation. -- Sanjeev Gupta +65 98551208 http://www.linkedin.com/in/ghane ___ 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.
