ABEM Terrameter SAS 1000 / SAS 4000
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8.2.3
2D and 3D Model Interpretation
Model interpretation accounting for 2D or 3D variation is not supplied with the system, but
third party software packages for resistivity data processing can be used for advanced
interpretation. Two such examples of programs are RES2DINV, SENS2DINV and RESIX
2DI, which perform smoothness-constrained inversion (inverse modelling). Please ask ABEM
or your authorised ABEM Distributor for details about resistivity interpretation packages that
are available.
For inverting the data with RES2DINV transfer the S4K files to a computer in the regular way
via the SAS1000/4000 Utility Software or use ERIGRAPH (version 2.9 or higher) for the
conversion
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. The latter will by default specify half the actual minimum electrode separation
on the second line of the data file for some electrode arrays (e.g. multiple gradient array,
dipole-dipole, pole-dipole), which forces RES2DINV to use a finer grid in the inversion
model. This is recommended as the inversion routine can have difficulties in handling the
increased information content in the data, compared to e.g. Wenner array data, which may
create artefacts if a coarser grid is used. Data is saved in the general four electrode format i.e.
array code 11, and sub-array code 0 (unspecified array) 15 (gradient array), 3 (dipole-dipole)
or 6 (pole-dipole).
Figure 19 shows an example plot of a 2D model interpretation section, inverted using
RES2DINV. Before plotting by ERIGRAPH it is necessary to convert from the iNV format to
RHO format, which can be done either in RES2DINV of ERIGRAPH. In cases with steep
topography the inverted model files from RES2DINV often benefit from converting to RHO
format from an XYZ file exported from RES2DINV, rather than converting directly from the
INV file. In order to include topography into the exported XYZ file it is necessary to plot the
model section including topography before exporting.
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At present there is a maximum of 6000 data points in the conversion routine.
