Order of operations: the following list is the order in which
the main operations are performed by VMODEL:
1) check that boundary nodes and velocities are listed
left to right, or re-order them
2) re-sample boundary nodes and velocities to increase or
decrease the number of model parameters
3) smooth layer boundaries and lateral velocity variations
4) check for small and large velocities, boundaries
crossing, low-velocity zones, negative vertical velocity
gradients, large changes in boundary slope, and large
vertical and lateral velocity gradients
5) plot the model, velocity profiles and RMS velocity
profile
6) write velocity model to the file v.out if it has been
changed
Low-velocity zones and pinchouts: low-velocity zones that occur
across one or more layers that have been pinched out will not
be detected.
External plot routines: VMODEL is self-contained except for the
graphics calls inside the following CALCOMP or CALCOMP-like plot
routines: PLOTS, PLOT, NUMBER, SYMBOL, LINE, EMPTY, ERASE, PLOTND.
The file pltlib.f contains ALL these routines (and a few other
less important ones used by the graphics system where the
code was developed) and it will be necessary to replace the "call"
statements within each of these with their equivalents in the
local graphics package.