ABEM Terrameter SAS 4000 / SAS 1000
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17
APPENDIX H. ERIGRAPH FILE FORMATS
17.1
INTRODUCTION
Erigraph is primarily designed to facilitate graphical presentation of CVES data (2D DC
resistivity surveying) and associated inverted model sections. The measured apparent
resistivities can be plotted as pseudosections in colour or grey scale. Inverted sections can be
plotted as continuous (smooth) plots or as rectangular blocks. 2D inversion must be carried
out using a separate inversion program, such as for example Res2dinv.
17.2
PSEUDOSECTION PLOTTING AND FILE FORMAT
The apparent resistivity data can be stored either in a conventional ASCII format with one set
of x, a, rho-a on each line or in the format used by Res2dinv (in both cases DAT filename
extension is assumed). For the latter format please refer to the manual of Res2dinv. Field data
files from the ABEM Lund Imaging System can be converted into DAT-files using
ERIGRAPH or the Terrameter SAS1000 / SAS4000 Utility Software.
In addition to the .DAT file the program searches for a file with .INF extension, which holds
information in the following format:
comment string
date of measurement
array type
blank
(line contents not used)
direction label left side
(
optional)
direction label right side (
optional)
n
l
no of marker labels (optional)
x[1] flag[1] marker text string[1]
label distance, type flag, text string
(optional)
x[2] flag[2] marker text string[2]
...
x[n
l
] flag[n
l
] marker text string[n
l
]
The topography can be automatically incorporated in the DAT file, if it is saved in an ASCII
file in the same directory as the OHM file to be converted. The topography file should have
the same filename as the data but with ALT extension. The file format is as follows:
x(1) alt(1)
x(2) alt(2)
...
...
x(n) alt(n)
17.3
INVERTED MODEL PLOTTING AND FILE FORMAT
Erigraph can plot inverted models in RHO-files (ASCII files) with the following format:
RHO-1 [IP]
nd Depth(1) Depth(1) ... Depth(nd)
x(1) rho(1,1) rho(1,2) ... rho(1,nd) [ip(1,1) ip(1,2) ... ip(1,nd)]
x(2) rho(2,1) rho(2,2) ... rho(2,nd) [ip(2,1) ip(2,2) ... ip(2,nd)]
...
...
x(nx) rho(nx,1) rho(nx,2) ... rho(nx,nd) [ip(nx,1) ip(nx,2) ... ip(nx,nd)]
/Model residuals:
[optional]
/Inversion type header:
[optional]
/IP parameter/unit
[optional]