Re: Filling in the Gaps (contour mapping)

[davidf(at)dfanning.com (David Fanning)]

Simon de Vet (simon@mathstat.dal.ca) writes:

> I am a new user to IDL (day 4 and having fun, now that I have some stuff
> working), so please forgive me if this is an obvious question.
> 
> I have data that I am contour plotting onto a world map. The data is
> spaced every 3.75 degrees in latitude and longitude. The longitude
> starts at 0 and ends at 356.25. Latitude runs from -88.125 to 88.125.
> 
> When plotted, the vast majority looks great. However, at the seam
> running through 0 longitude, the two edges are not connected. While it
> is less obvious, I assume that a similar problem is occuring at the
> poles. The poles are not much of a concern, since the top 10 degrees are
> cut off in a Mercator projection anyways...
> 
> Since the data does not connect, I cannot use a filled contour plot,
> which is one of my goals.
> 
> Any suggestions? Is there an easy way to do this, or will I have to have
> the first longitudinal values repeated at the end of the list? It seems
> that IDL is not recognizing that 0 degrees and 360 degrees are the same
> thing.

Humm. I don't see any disconnect when I do this with or without
contour filling. Better let us have a peak at this part of
your code. :-)

And if you are doing filled contours, you better have a look
at my web page before you get too much further along. There
are a couple of things there you might need that you won't 
find in your IDL documentation. :-)

I'd start with this one, but there are a couple you should look
at:

   http://www.dfanning.com/tips/contour_hole.html

Cheers,

David

-- 
David Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438 E-Mail: davidf@dfanning.com
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