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Contouring data over maps [message #12469]

Mon, 03 August 1998 00:00

Callie Hall
Messages: 1
Registered: August 1998

Junior Member

Hello,

I am currently developing an application in IDL that needs to
draw contour plots
over a map. My data is irregularly gridded, and very sparse. What I
need to know
is how to make IDL respect the land/sea continental boundries when I
plot my
interpolated data. I can only currently clip my contour plot to a
latitude/longitude range..
I need to know how to make my contour conform to the coastlines.

Please help,

Jason Hasenbuhler

hasenbuh@rex.cs.tulane.edu

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Re: Contouring data over maps [message #12653 is a reply to message #12469]

Mon, 10 August 1998 00:00

mgfreeman
Messages: 1
Registered: August 1998

Junior Member

Hi Jason

Apologies if something similar appears, this is the first time I've tried to
post and I don't think it worked on Friday (and of course I forgot to keep a
copy so I'm writing this again!).

About 2 years ago I did something very similar, contouring temperature and
salinity in the Eastern Mediterranean. My gridded dataset had Cyprus sat
right in the middle of the data. To stop contour extrapolating/interpolating
across land I assigned NaN (IEE not a number) values to the grid points on
land. This stopped contour lines across land and also stopped any data
'slant' due to using 0's (or any other 'fudge' value). This method has one
drawback that you can't fill the contours as they have to be closed.

I wrote a simple point and click program to assign the NaN values. If you
like I can try and dig out the code (email me!).

Hope this helps

Mark Freeman

In article <35C7589E.C37A0F1C@rex.cs.tulane.edu>,
hasenbuh@rex.cs.tulane.edu wrote:
> Hmm

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