[time-nuts] sub-minute time-precision in court-case

Tom Miller tmiller at skylinenet.net
Wed Sep 4 00:15:19 UTC 2013


----- Original Message ----- 
From: "Jim Lux" <jimlux at earthlink.net>
To: "Poul-Henning Kamp" <phk at phk.freebsd.dk>
Cc: "Discussion of precise time and frequency measurement" 
<time-nuts at 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 at 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 




More information about the Time-nuts_lists.febo.com mailing list