sub-minute time-precision in court-case
Tom,
Did you ever reset that thing to the correct time? =)
Bob
From: Tom Van Baak tvb@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
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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."
On 9/3/13 11:21 AM, Poul-Henning Kamp wrote:
In message 5225F8AF.60807@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.
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.
----- Original Message -----
From: "Jim Lux" jimlux@earthlink.net
To: "Poul-Henning Kamp" phk@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.60807@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
Re the PSAP timekeeping Requirement: See NENA 04-002, Traceable UTC
Source, Master Clock Specification
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.
On Wed, Sep 4, 2013 at 6:19 AM, Tom Van Baak tvb@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
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
phk@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.
On 9/3/13 10:11 PM, Sanjeev Gupta wrote:
On Wed, Sep 4, 2013 at 6:19 AM, Tom Van Baak tvb@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.
And in California, cannot be operated by those under 18, even with the
hands free capability.
In message 522735C1.6020004@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
phk@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.