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Home page > Instruments and Data > Instrument Responses > SAC POLEZERO format

SAC POLEZERO format

by Wayne Crawford - 17 October 2011

SAC pole-zero files provide poles, zeros and a constant that transformed the data from the "input units" (a displacement) to the "output units" (counts). SEED specifies displacements in meters, whereas SAC pole-zero files give displacements in nanometers. To avoid confusion, we include these SAC-accepted comment lines in the file:

* INPUT UNIT        : NM
* OUTPUT UNIT       : COUNTS
* INSTTYPE          : ------------------------------

L-28 geophone

* INPUT UNIT        :  NM
* OUTPUT UNIT       : COUNTS
* INSTTYPE          : Sercel L-28 geophone with LC2000 logger
ZEROS 3
POLES 2
   13.18    -25.02
   13.18     25.02
CONSTANT 4.68066

L-22 geophone

* INPUT UNIT        :  NM
* OUTPUT UNIT       : COUNTS
* INSTTYPE          : Sercel L-22 geophone with LC2000 logger
ZEROS 4
POLES 3
   8.886    -8.886
   8.886     8.886
  -6.667         0
CONSTANT 4.04877

Trillium T240

* INPUT UNIT        :  NM
* OUTPUT UNIT       : COUNTS
* INSTTYPE          : Trillium T240 with LC2000 logger
ZEROS 5
    -108         0
    -161         0
POLES 7
-0.01815  -0.01799
-0.01815   0.01799
    -173        -0
    -196      -231
    -196       231
    -732     -1415
    -732      1415
CONSTANT 7.18637e+08

HiTech modified HTI-90U hydrophone

* INPUT UNIT        : PA
* OUTPUT UNIT       : COUNTS
* INSTTYPE          : modified HiTech HTI-90U hydrophone with LC2000 logger (unverified)
ZEROS 1
POLES 1
  -6.667         0
CONSTANT 54805.6

DPG #5004, logger 21

* INPUT UNIT        : PA
* OUTPUT UNIT       : COUNTS
* INSTTYPE          : DPG with LC2000 logger
* COMMENT           : DPG S/N #05004
* COMMENT           : LOGGER S/N #21
ZEROS 2
POLES 2
-0.0483322         0
-0.017952         0
CONSTANT 495

DPG #5004, logger 21

* INPUT UNIT        : PA
* OUTPUT UNIT       : COUNTS
* INSTTYPE          : DPG with LC2000 logger
* COMMENT           : DPG S/N #05018
* COMMENT           : LOGGER S/N #22
ZEROS 2
POLES 2
-0.0628319         0
-0.0139626         0
CONSTANT 510

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