SUMMARY

Synchronizes the reference times of all files in memory.

SYNTAX

SYNCHRONIZE {ROUND {ON|OFF}} {BEGIN {ON|OFF}}

INPUT

ROUND {ON}:	Turn begin time rounding on. When this opotions is on, the begin times for each file are rounded to the nearest multiple of the sampling interval.
ROUND OFF:	Turn begin time rounding off.
BEGIN {ON}:	Sets begin time of each file to zero.
BEGIN OFF:	Maintains the GMT values of the reference times.

DEFAULT VALUES

SYNCHRONIZE ROUND OFF BEGIN OFF

DESCRIPTION

This command synchronizes the references times for all files in memory. It determines the latest starting time of all files by examining their reference times and beginning offset times. This latest starting time then becomes the reference time for ALL of the files in memory. New values for all of the offset times (B, E, A, Tn, etc.) for each of the files are then calculated.

This command is useful when a set of files have different reference times and you want to use the CUT or XLIM command to analyze or plot portions of them. Once they have been synchronized to the same reference time, the cuts will then refer to the exact same GMT time window. If the BEGIN option is used, GMT values of reference times are not preserved. The BEGIN option sets the kztime of all files the same, it sets the kzdate of all files the same, and it sets the begin time of all files to zero. Other reference points retain their relation to the begin time of the file.

EXAMPLES

Assume you read two files into memory with different reference times:

SAC> READ FILE1 FILE2
SAC> LISTHDR B KZTIME KZDATE

    FILE: FILE1
    -----------
           B = 0.
      KZTIME = 10:38:14.000
      KZDATE = MAR 29 (088), 1981

    FILE: FILE2
    -----------
           B = 10.00
      KZTIME = 10:40:10.000
      KZDATE = MAR 29 (088), 1981

The files have the same reference date but different reference times and different beginning offsets. Now if you execute the SYNCHRONIZE command followed by another LISTHDR you would find:

SAC> SYNCHRONIZE
SAC> LISTHDR

    FILE: FILE1
    -----------
           B = -126.00
      KZTIME = 10:40:20.000
      KZDATE = MAR 29 (088), 1981

    FILE: FILE2
    -----------
           B = 0.
      KZTIME = 10:40:20.000
      KZDATE = MAR 29 (088), 1981

Now the files in memory have the same reference time which is the beginning of the later file. If there had been any defined time markers in these headers, their values would be adjusted so that they point to the same time as before.

HEADER CHANGES

NZYEAR, NZJDAY, NZHOUR, NZMIN, NZSEC, NZMSEC, B, E, A, O, Tn.

LATEST REVISION

May 15, 1987 (Version 10.2)