.de BR
.in 0
.in +8n
.ti -3n
..
.Th                               SYNCHRONIZE
.S2 SUMMARY:
Synchronize reference times

SYNChronize o | a | b | e | o

.S2 INPUT:
o        : set the reference time as the origin time
.BR
a        : set the reference time as the P arrival time
.BR
b        : set the reference time as the fist sample

.S2 DESCRIPTION:
The purpose of this command is to make the reference times the same
for all traces in memory. It determines the earliest absolute starting time
of all files, and sets the B time of that file to 0.0. The B times of other
files are then always >0 =. Although SAC used the latest start time, ours
ensures that B is never set to the magic \-12345.
.sp
As a result of this operation, any marked times, e.g., B, E, O, A, Tn, F are
result so that the absolute time of these markers are not changed.
.sp
A previous use for this was to ensure that MARKALL and ROTATE will work
properly. GSAC works with absolute time.
.sp
The reason for the O ( oh - origin time ) option is to set the origin time
as the reference time. This is useful when documenting events - just use saclhdr with the -KZDATE -KZTIME options. The reuslt is that the arrival offsets A, T0, ..., T9 will then be the travel times. The sequence
.na
.nf
     GSAC> set o
     GSAC> set a P_travel time
.fi
.ad
This is an easy way to set the phase arrival time. Otherwise one would ahve to add the travel time to the origin time offset.
.sp
The reason for the A option is to align waveforms on the P arrival in a two step process. First this option changes the reference times so that the A header value is zero. Then one can use a 
.BR
ch NZYEAR year NZJDAY jday NZHOUR hour NZMIN min NZSEC sec NZMSEC msec
.BR
to change the reference time. This is one way to overcome bad timing on the individual channels.
.S2 "SEE ALSO":
       

