In a message dated 06/05/2005, lcochrane@.............. writes:

Bryan,
With the Garmin GPS receiver your timing should be accurate  to within one or 
two 
milliseconds.
Regards,
Larry  Cochrane



Hi Larry,
 
    Do you have any figures, or preferably  measurements, for the time delay 
produced by the filters on your amplifier  boards, please?
    
    Putting in the values for an 8th order 5 Hz  Butterworth low pass filter 
suggest that the delay is likely to be ~160  milli sec below 2 Hz, peaking to 
about 280 milli sec at 5 Hz.
 
    These delays, while swamping any timing errors, are  unlikely to give 
significant errors in general Earthquake location. However,  since an 8 pole 1.5 
Hz filter can produce a lag of over 1/2 second, we may  sometimes need to take 
filter delays into account, more particularly for local  events.
 
    Regards,
 
    Chris Chapman






In a message dated 06/05/2005, lcochrane@.............. writes:
<=
FONT=20
  style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20
  size=3D2>Bryan,
With the Garmin GPS receiver your timing should be accu=
rate=20
  to within one or two 
milliseconds.
Regards,
Larry=20
Cochrane


Hi Larry,
 
    Do you have any figures, or preferably=20
measurements, for the time delay produced by the filters on your amplifier=20
boards, please?
    
    Putting in the values for an 8th order 5 H=
z=20
Butterworth low pass filter suggest that the delay is likely to be ~160=
=20
milli sec below 2 Hz, peaking to about 280 milli sec at 5 Hz.
 
    These delays, while swamping any timing errors,=
 are=20
unlikely to give significant errors in general Earthquake location. However,=
=20
since an 8 pole 1.5 Hz filter can produce a lag of over 1/2 second, we may=20
sometimes need to take filter delays into account, more particularly for loc=
al=20
events.
 
    Regards,
 
    Chris Chapman