Keith Payea kpayea@..............
Subject: RE: Is our quake time correct?
Hello All:
=20
First, most GPS receivers do correct for the GPS:UTC leap seconds issue, an=
d output UTC. However, it is possible on some of them to change a setting =
and get raw GPS time. Since the offset is 15 seconds, it=E2=80=99s pretty =
easy to check your receiver.
=20
Secondly, most of the =E2=80=9CNTP=E2=80=9D software toys available for fre=
e are really doing SNTP (Simple Network Time Protocol) which does very litt=
le except ask for the current time once in a while and jam it into your com=
puter=E2=80=99s clock. Real NTP compensates for transmission delays and us=
es multiple servers as inputs to a very complex filtering algorithm to remo=
ve all kinds of errors.
Meinberg offers a full NTP implementation for windows that actually steers =
the clock and does all of the filtering. You can get it here: http://www.me=
inberg.de/english/sw/ntp.htm
=20
Hi Keith,
=20
Another program that amateur seismologists might like to try is the one=
used for our schools programs, particularly when they are using the 'older=
' type computers and operating systems. It is called AboutTime See http://w=
ww.arachnoid.com/abouttime/ for downloads and notes. It calls up a server, =
gets the current time, then 'pings' the server to measure the transmission =
delay and updates the computer clock. If you update your computer clock at =
55 mins to every hour, even the lousy clocks fitted to a lot of computers c=
an be persuaded to keep adequately good time ! If your system is not perman=
ently on line, you can buy inexpensive WWVB radio controlled clocks which u=
sually run on two AA batteries and may have only a 20 milli second error. S=
ee http://www.nist.gov/pml/div688/grp40/radioclocks.cfm MSF and DCF77 radi=
o clocks are available in Europe.=20
=20
Regards,
=20
Chris Chapman
=
Keith Payea kpayea@..............<=
/A>
Subject: RE: Is our quake time correct?
Hello=
All:
=
;
First=
, most GPS receivers do correct for the GPS:UTC leap seconds issue, and out=
put UTC. However, it is possible on some of them to change a setting =
and get raw GPS time. Since the offset is 15 seconds, it=E2=80=99s pr=
etty easy to check your receiver.
=
;
Secon=
dly, most of the =E2=80=9CNTP=E2=80=9D software toys available for free are=
really doing SNTP (Simple Network Time Protocol) which does very little ex=
cept ask for the current time once in a while and jam it into your computer=
=E2=80=99s clock. Real NTP compensates for transmission delays and us=
es multiple servers as inputs to a very complex filtering algorithm to remo=
ve all kinds of errors.
Hi Keith,
Another program that amateur seismologists mig=
ht like to try is the one used for our schools programs, particularly =
when they are using the 'older' type computers and operating systems. =
It is called AboutTime See =
http://www.arachnoid.com/abouttime/ for downloads and notes. It ca=
lls up a server, gets the current time, then 'pings' the server to measure =
the transmission delay and updates the computer clock. If you update your c=
omputer clock at 55 mins to every hour, even the lousy clocks fit=
ted to a lot of computers can be persuaded to keep adequately good tim=
e ! If your system is not permanently on line, you can buy inexpensive=
WWVB radio controlled clocks which usually run on two AA batteries an=
d may have only a 20 milli second error. See http://www.nist.gov/pml/div688/grp4=
0/radioclocks.cfm MSF and DCF77 radio clocks are available i=
n Europe.
Regards,
Chris Chapman