bathymetry overlay

[Keith Lindsay <klindsay@xxxxxxxxxxxx>]

Greetings,

I have a gridded dataset which was generated from ship measurements. The
gridding procedure extended the data below the sea floor. I would like to
overlay a bathymetry mask on contour plots of the gridded data. I would
like to the mask to be from ship measurements of sea bottom, not a
regridding of this. I am attempting to use the command polygon, but have
run into a snag. I am trying the following

shade DIC
polygon/over/nolab/palette=white LAT_CAST , BOTTOM_CAST*(-1)

DIC is a gridded variable and LAT_CAST and BOTTOM_CAST are latitude
(degrees) and sea bottom values (meters). This is not what I want because
the polygon command is closing the sequence of lat,bottom values and
subsequently masking large portion of the shaded figure, not the land.

What I would like to do for the polygon arguments is something like

{-90, -90, LAT_CAST[i=1], LAT_CAST, LAT_CAST[i=($imax)], 90, 90},
{-6000, 0, 0, BOTTOM_CAST, 0, 0, 6000}

The symbol imax denotes  the number of casts.

The idea I'm trying to express is to pad the data with bogus points so
that when the polygon is filled, it is filling in the plot where there is
land, or beyond the range of data. I cannot figure out how to combine
constants and variables though. Is this possible?

If someone has suggestions for another way to do the bathymetry mask,
please let me know.

Thanks,
Keith

************************************************************************
Keith Lindsay         http://www.cgd.ucar.edu/oce/klindsay/klindsay.html
email: klindsay@cgd.ucar.edu    phone: 303-497-1722    fax: 303-497-1700