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.Th                                    CHANGEHEADER
.S2 SUMMARY:
Change header values in memory

ChangeHeader [ name value ]

.S2 INPUT:
name     : SAC header name
.BR
value    : New value for that header variable

.S2 DESCRIPTION:
This commands lets one change many of the header values associated with a trace.
If more than one trace is in memory, then all header variables are updated.
The following listing gives the header names that can be changed:
.sp
.nr 
.na
Reals: DELTA, DEPMIN, DEPMAX, SCALE, ODELTA, B,
E, O, A, FMT, T0, T1,
T2, T3, T4, T5, T6, T7,
T8, T9, F, RESP0,
RESP1, RESP2, RESP3, RESP4, RESP5, RESP6,
RESP7, RESP8, RESP9, STLA, STLO, STEL,
STDP, EVLA, EVLO, EVEL, EVDP,
USER0, USER1, USER2, USER3, USER4, USER5,
USER6, USER7, USER8, USER9, DIST, AZ,
BAZ, GCARC, SB, SDELTA, DEPMEN, CMPAZ,
CMPINC, XMINIMUM, XMAXIMUM, YMINIMUM, YMAXIMUM, ADJTM   
.sp
Integers: NZYEAR, NZJDAY, NZHOUR, NZMIN, NZSEC, NZMSEC,
N NINF, NHST, NPTS, NSNPTS, NSN,
NXSIZE, NYSIZE, IFTYPE, IDEP, IZTYPE,
IINST, ISTREG, IEVREG, IEVTYP, IQUAL, ISYNTH,
IHDR12, IHDR13, IHDR14, IHDR15, IHDR16, IHDR17,
IHDR18, IHDR19, IHDR20, LPSPOL, LOVROK, LCALDA,
.sp
Strings: KSTNM, KEVNM, KHOLE, KO, KA, KT0,
KT1, KT2, KT3, KT4, KT5, KT6,
KT7, KT8, KT9, KF, KUSER0, KUSER1,
KUSER2, KCMPNM, KNETWK, KDATRD, KINST
.fi
.ad
.sp
NOTE THAT ANY ATTEMPT TO CHANGE NVHDR or NPTS IS IGNORED
.sp
Because SAC permits something like
.sp
   ch o 10
.sp
   ch o gmt 2004 123 10 20 30 500
.sp
The command parsing is complicated. GSAC handles this by internally 
concatenating the o and gmt to form the new GSAC ogmt. GMT introduces the
following time commands:
.sp
Setting GMT Time: OGMT, AGMT, T0GMT, T1GMT, T2GMT, T3GMT,
T4GMT, T5GMT, T6GMT, T7GMT, T8GMT, T9GMT
.sp
Also since it is often inconvenient to determine the day of the year, GSAC permits entries of the form
.sp
   ch OCAL 2004 05 02 10 20 30 500
.sp
   ch o cal 2004 05 02 10 20 30 500
.sp
Setting Calendar Time: OCAL, ACAL, T0CAL, T1CAL, T2CAL, T3CAL,
T4CAL, T5CAL, T6CAL, T7CAL, T8CAL, T9CAL
.sp
NOTE You can assign values to USER1 and USER2 if followed by a WRITEHEADER. However if you follow by a WRITE, then the USER1 and USER2 fileids will be the minimum and maximum filter periods.  THIS WAS A DESIGN DECISION.

.S2 "SEE ALSO":
WriteHeader, ListHeader
       

