Re: contour boundaries

[Med Bennett <mbennett(at)indra.com>]

Remy Luerssen wrote:

> 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

Hi Remy,

Is your coastline concave towards land?  You may have to use the MIN_VALUE keyword
- I usually force areas that I don't want contoured as 0, or -999, or something
else that is below the data range, and use the min_value = 0 keyword.  I don't know
if using NaNs really works or would work wth the min_value keyword.