[Antelope] (no subject)

[Jeff McGuire]

Hi All, 

I'm trying to understand how station elevations are dealt with in the 
travel time calculations for 1-d models.  It looks to me like in
Gary Pavlis's routine tt1dcvl.c, if the station has an elevation that
is within the first layer, then the top of the first layer is reset
to the station elevation.  However, if the station elevation is in
the second layer, then no correction is applied: Relevant lines of code:

if(x->receiver.z < mod->ztop[1])
		mod->ztop[0] = x->receiver.z; 
	else
	{
		register_error(0,"Warning (ttlvz_slowness_exec):  elevation correction
error\nStation elevation %lf lies below first layer depth %lf\nElevation
ignored\n",
			x->receiver.z, mod->ztop[1]);

My question is what's the appropriate way to define the velocity model
layers elevations in the vmodel_example.mod1d database.  For instance,
if 
one was dealing with stations at positive 500m, 250m, and 0m, then
should the first value of "depth" in the .mod1d table be -500m, and the
second value be  something > 0m ?

Any suggestions on the cleanest way to implement this for ocean bottom
data with elevations of -3000m.  The first depth value should be above
the 
shallowest station and the second depth value should be bellow the
deepest?

Thanks for your help,
Jeff