Choice of inversion
Select one of four radio-buttons to indicate which type of inversion
algorithm should be used (iatype in the manual).
Some information on what these choices mean can be found in the UBC-GIF
on linear inversion (section 25).
NOTES: GCV is the default because the errors on data are not often
well-known. However the GCV method sometimes produces models that are somewhat
"over-fit". This means there is too much structure. One approach that works
sometimes is to perform an inversion on a line of data using the GCV criterion,
then observe the resulting Beta
values that are determined along the line. Choose a suitable value
that might work for most of the line and run a second inversion run using
the "fixed trade-off" option where the value of Beta you chose is
specified in the "trade-off" parameter box. This is not guaranteed
to work, but it is one idea.
Select "fixed trade-off" to specify a fixed, user-supplied value for the
trade-off parameter (enter this value in the box labelled "trade-off").
Select "line search" to specify that the trade-off parameter will be chosen
by means of a line search so that a target misfit is achieved (or, if this
is not possible, then the smallest misfit).
Select "GCV" to specify that the trade-off parameter will be chosen using
the GCV criterion. See Notes below.
Select "L-curve" to specify that the trade-off parameter will be chosen
using the L-curve criterion.