ABEM Terrameter SAS 1000 / SAS 4000
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If the multi-channel dipole-dipole or pole-dipole protocols mentioned in this document are
used, it is necessary to do roll-along twice without adding new cable at end of line (see Figure
13). This depends on that these protocols are designed to avoid unnecessary repetition of
measurements, and still get as much data as possible. Such a procedure need not be
considered for single channel dipole-dipole or pole-dipole protocols. Notice that even if this
procedure is used duplicate data points can occur for multi-channel pole-dipole protocols after
roll-along.
For a cable set of 4 cables with 16 electrode take-outs each it is simpler. For nested electrode
arrays (such as Wenner, Schlumberger and multiple gradient) all possible measurements can
be taken with all 4 cables in one go. Hence all electrodes must be connected at the start.
Furthermore, there must be no overlapping of electrode take-outs at the cable intersections. It
is only for dipole-dipole and pole-dipole type of arrays measured with multi-channel
equipment that it is motivated to consider using measurement protocols that require roll-along
move of the instrument without adding new electrodes at the end of a surveying line in order
to optimise the use of the multi-channel capability.
Figure 12. Cable arrangement at the last measurement station in a Wenner, Schlumberger or
multiple gradient array roll-along survey, where the last cable is excluded.
Figure 13. Cable arrangement at the last measurement station in a dipole-dipole or pole-
dipole roll-along survey, where the last two cables are excluded.
