contour boundaries

[onlyremy(at)hotmail.com (Remy Luerssen)]

I am having troubles with a contouring program in IDL.  I have gridded in situ 
measurements taken from stations throughout the Gulf of Maine.  I am contouring 
the data over a map of the Gulf of Maine.  In order to take into consideration 
where the land is, the gridded in situ data was changed to NaN where there was 
land.  The problem that I am having is that the contouring program is not 
recognizing the boundaries of the dataset.  There are contouring lines going 
through the land, eventhough the data its self are NaNs.  But the kicker is 
that there is a data boundary that does not border the coast (the stations end 
but not due to land construct) that is recognized.  The contour lines stop 
like they should.  Any ideas what is going on?

I would appreciate any suggestions!  

Thanks,

Remy