Thread: SAC format questions

- Most SAC reading code out there works with version '6' of the header,
how common are other versions of the header, does 6 cover the vast
majority?

Brian Savage found the attached file and sent it to me.

The short version is that I do not think we have to think about earlier
versionsSAC version history

History: In reverse order
* 821001: Header version 6 installed.
* 801018: Header version 5 installed.
* 800809: Fixed bug with headers of files from Octopus.
* 800510: Header version 4 installed.
* 800105: Original Prime version.

Version 1: "Original Prime Version"
* I am assuming this as Version 1 as it was not documented in updhdr.c

Version 2: changed the values in each of the header field types
* used to represent an undefined state. Previously they were all
* equivalent to the ascii 'UNDEF'. Now they are:
* - FUNDEF = -12345. for floating point fields.
* - NUNDEF = -12345 for integer fields.
* - IUNDEF = -12345 for selected value fields.
* - KUNDEF = 'UNDEF' for alphanumeric fields.
* - no value for undefined logical fields.
* - Version 1 was never supported on the Prime.

Version 3:
* - added FINI in FHDR(40).
* - added SB in FHDR(55).
* - added SDELTA in FHDR(56).
* - added FMEAN in FHDR(57).
* - replaced ICOMP in IHDR(4) and HORZO in FHDR(21)
* with CMPAZ in FHDR(58), CMPINC in FHDR(59),
* KCMPNM in KHDR(1,6), and LPSPOL in LHDR(2).
* - possible values of ICOMP were IRADNV=23, ITANNV=24,
* IRADEV=25, ITANEV=26, INORTH=27, IEAST=28,
* IHORZA=29, IDOWN=30, and IUP=31.

Version 4:
* - added LOVROK in LHDR(3).
* - moved NZHOUR from NHDR(5) to NHDR(4).
* - moved NZMIN from NHDR(6) to NHDR(5).
* - equivalenced NZDTTM array to NZYEAR in NHDR(2).
* - changed entire KHDR array. Before each entry was 24 characters
* in length. Now they may be any multiple of 8 characters in
* length.
* KHDR was changed to a 1 dimensional array but the length was
* not changed.
*
* variable old_loc new_loc new_len
* -------- ------- ------- -------
* KSTNM 1 1 1
* KEVNM 4 2 2
* KHOLE 7 4 3
* KZTIME 10 7 2
* KZDATE 13 9 3
* KCMPNM 16 12 3
* KUSER NEW 13 3

Version 5:
* - Changed alphanumeric undefined fields from 'UNDEF' to '-12345'.
* - Changed all KHDR fields from dimensioned CHAR*8 variables
* to non dimensioned variables of correct character length.
* - Decreased size of KHOLE from 24 to 8 characters.
* - Changed KUSER of length 24 char. to KUSER0, KUSER1, and KUSER2
* each of length 8 char. Moved them from KHDR(13) to KHDR(18).
* - Deleted KZDATE, KZTIME and KCMPNM.
* - Added 13 new alpha fields: KO, KA, KTn (n=0,9), and KF.
* - Current arrangement of KHDR is therefore:
* variable old_loc new_loc new_len
* -------- ------- ------- -------
* KSTNM 1 1 1
* KEVNM 2 2 2
* KHOLE 4 4 1
* KO NEW 5 1
* KA NEW 6 1
* KTn NEW 7-16 1 each
* KF NEW 17 1
* KUSER0 13 18 1
* KUSER1 14 19 1
* KUSER2 15 20 1
* KHDR21 EMPTY 21 1
* KHDR22 EMPTY 22 1
* KHDR23 EMPTY 23 1
* KHDR24 EMPTY 24 1
* - Moved NSNPTS from NHDR(10) to NHDR(11).
* - Moved NPTS from NHDR(1) to NHDR(10).
* - Changed size of NZDTTM array from 4 to 6.
* - Moved NZDTTM and NZYEAR from NHDR(2) to NHDR(1).
* - Moved NZJDAY from NHDR(3) to NHDR(2).
* - Moved NZHOUR from NHDR(4) to NHDR(3).
* - Moved NZMIN from NHDR(5) to NHDR(4).
* - Converted ZSECS in FHDR(5) to NZSEC in NHDR(5) and
* NZMSEC in NHDR(6).
* - Moved FINI from FHDR(40) to FHDR(21).

Version 6:
* (1) Added LCALDA. If .TRUE. distance/azimuth are always
* recomputed each time file is read.