Antenna separation GSSI Structure Scan XT device

[emanuelhuber]

Anyway I have some real data files from a GSSI Structure Scan XT device (here attached). To me the antenna separation should be about 80 mm in that device. But importing datas I get 0:

 str(x1)
 Formal class 'GPR' [package "RGPR"] with 29 slots
   ..@ version     : chr "0.2"
   ..@ data        : num [1:510, 1:903] 0.00041 0.000358 0.00031 0.000349
 0.000295 ...
   ..@ traces      : int [1:903] 1 2 3 4 5 6 7 8 9 10 ...
   ..@ depth       : num [1:510] 0 0.00803 0.01607 0.0241 0.03214 ...
   ..@ pos         : num [1:903] 0 0.00125 0.0025 0.00375 0.005 ...
   ..@ time0       : num [1:903] 0 0 0 0 0 0 0 0 0 0 ...
   ..@ time        : num [1:903] 1.43e+09 1.43e+09 1.43e+09 1.43e+09
 1.43e+09 ...
   ..@ fid         : chr [1:903] "" "" "" "" ...
   ..@ ann         : chr(0)
   ..@ coord       : logi[0 , 0 ]
   ..@ rec         : logi[0 , 0 ]
   ..@ trans       : logi[0 , 0 ]
   ..@ coordref    : num(0)
   ..@ freq        : num 0
   ..@ dz          : num 0.00803
   ..@ dx          : num 0.00125
   ..@ antsep      : num 0
   ..@ name        : chr "FILE__008"
   ..@ description : chr ""
   ..@ filepath    : chr "rawGPR/FILE__008.DZT"
   ..@ depthunit   : chr "ns"
   ..@ posunit     : chr "cm"
   ..@ surveymode  : chr "reflection"
   ..@ date        : chr "2015-03-05"
   ..@ crs         : chr(0)
   ..@ proc        : chr(0)
   ..@ vel         :List of 1
   .. ..$ : num 0.12
   ..@ delineations: list()
   ..@ hd          :List of 24
   .. ..$ TAG       : int 2047
   .. ..$ OFFSETDATA: num 131072
   .. ..$ NSAMP     : int 512
   .. ..$ BITS      : int 32
   .. ..$ ZERO      : int 3
   .. ..$ SPS       : num 250
   .. ..$ SPM       : num 800
   .. ..$ MPM       : num 5
   .. ..$ POSITION  : num -0.411
   .. ..$ RANGE     : num 4.11
   .. ..$ NPASS     : int 0
   .. ..$ DATE      : chr "2015-03-05"
   .. ..$ TIME      : chr "27:01:00"
   .. ..$ OFFSETTEXT: int 512
   .. ..$ NTEXT     : int 0
   .. ..$ PROC      : int 128
   .. ..$ NPROC     : int 13
   .. ..$ NCHAN     : int 1
   .. ..$ EPSR      : num 6
   .. ..$ TOP       : num 0.0246
   .. ..$ DEPTH     : num 0.246
   .. ..$ ANT       : chr "none"
   .. ..$ VSBYTE    : int 28672
   .. ..$ MRKS      : int [1:903] 0 0 0 0 0 0 0 0 0 0 ..
```.
could be that not every device is going to write that parameter into the
file?
Which measure unit has that parameter? Meter [m] or millimeter [mm]. In
other words: should I put there 0.08 or 80 if the antenna separation 80 mm
is?

Thank you very much.
Davide

[emanuelhuber]

The .dzt files do not hold any information about antenna separation distance, see SIR 30 manual, page 106: https://www.geophysical.com/wp-content/uploads/2017/10/GSSI-SIR-30-Manual.pdf

You need to set manually the antenna separation in the unit of A@depthunit:

antsep(A) <- 0.08   # m

Note that you can change the "depthunit" manually but you have to adapt (if necessary the trace position as well as the antenna separation distance): depthunit(A) <- "m"