A hybrid method for modeling marine controlledsource
electromagnetics, simplified integral equation (IE) (SIE)
modeling, has shown very promising results in 2-D. The computational
gain of SIE is very large for large problems in 3-D.We assess
the accuracy and range of validity of SIE modeling in 3-D through
order-of-magnitude analysis and through an extensive numerical
comparison with rigorous IE modeling. A previously proposed
order-of-magnitude analysis results in a dimensionless parameter
which is easy to use as an a priori indicator for when SIE is valid.
Unfortunately, this parameter is found to be sometimes inconsistent
with our numerical results. Order-of-magnitude analysis for
Maxwell’s equations is then reassessed in an attempt to rectify the
shortcomings of the parameter adapted from the work “Electrical
Impedance Tomography” by Cheney et al. The dimensionless
parameter resulting from the novel order-of-magnitude analysis is
found to have generally good predictive capability. Unfortunately,
this parameter is not suitable for deciding a priori if the use of
SIE is justified for a particular case, since it depends on numerical
results from IE modeling. For future use of SIE, it is therefore
recommended to compare the problem characteristics of the case
at hand with those covered by the extensive numerical comparison
in this paper. From the numerical investigation, it is found that the
accuracy of SIE is very good for resistive targets and for frequencies
lower than about 10 Hz. For conductive targets, the accuracy
is mostly very good for frequencies lower than about 5 Hz but
somewhat more dependent also on other problem characteristics.