| Contour plots on maps [message #19998] |
Mon, 15 May 2000 00:00  |
Simon de Vet
Messages: 36
Registered: May 2000
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Member |
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I have been trying to plot some contour maps onto different map
projections, and for the most part, it is working. I have been having
some troubles, however...
Sometimes, contours try to connect across the map, cutting diagonally
across other lines, instead of terminating at the edges. These lines are
not at the borders of the data, merely at the borders of the current
projection.
I have also had troubles with filled contours on map projections
(Mercator, in my case). While filled plots look nice with no map
projection used, with Mercator they are overwritten with white blocks at
times, leaving only a few spots of colour. The help says that using map
projections can cause filled contour troubles... Are there any
workarounds?
Thanks
Simon, a new user.
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| Re: Contour plots on maps [message #20131 is a reply to message #19998] |
Mon, 22 May 2000 00:00  |
Martin Schultz
Messages: 515
Registered: August 1997
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Senior Member |
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Hi Simon,
what helped me often in these situations is to make sure that the
data and
your map projection are "aligned" correctly, i.e. for a regional plot
(using the
LIMIT keyword to MAP_SET) you shouldn't have (much) more data than what
fits onto
the map, and in case you wrap your map around the dateline or play
similar tricks,
you should also shift your data accordingly. Although CELL_FILL covers
many of these
situations, I still consider it a somewhat dirty trick and I am only
happy after my plots appear similar with or without CELL_FILL.
David: here is what could be the tip of the year 2000 (although not as
simpel and short as the decomposed thing): "Why are my (filled) contours
so messy?"
Cheers,
Martin
Simon de Vet wrote:
>
> David Fanning wrote:
>
>> There are several articles that you will really want to
>> read on my web page, but I would start with this one,
>> because you definitely have "holes" in your contour plots:
>
> I found this site, and already have incorporated the solution into my code.
> If I plot my filled contours without a map projection, it plots beautifully,
> with no holes or gaps.
>
> This is the problem: first, the lowest few contours are filled in. Then they
> are all overwritten in white, and the next are filled in. These are also
> whited out, and the last couple are plotted. Only the last ones are visible
> when the plotting is complete.
>
> I am outputting all my plots to postscript files, and not to the screen
>
> I have also tried changing the centre of the plot, as you mentioned, so that
> the data border corresponds to the plot border (Greenwhich on the edge,
> instead of the middle.) This eliminates the odd diagonal lines, but does
> nothing to the filled contour troubles.
>
> These problems occur for all map projection types, and never if map
> projection is turned off.
>
> Simon
--
[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[ [[[[[[[
[[ Dr. Martin Schultz Max-Planck-Institut fuer Meteorologie [[
[[ Bundesstr. 55, 20146 Hamburg [[
[[ phone: +49 40 41173-308 [[
[[ fax: +49 40 41173-298 [[
[[ martin.schultz@dkrz.de [[
[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[ [[[[[[[
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| Re: Contour plots on maps [message #20221 is a reply to message #19998] |
Mon, 22 May 2000 00:00 |
davidf
Messages: 2866
Registered: September 1996
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Senior Member |
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Martin Schultz (martin.schultz@dkrz.de) writes:
> David: here is what could be the tip of the year 2000 (although not as
> simpel and short as the decomposed thing): "Why are my (filled) contours
> so messy?"
We could use a whole tutorial on filled contour plots. I'd be
willing to write some notes up in PDF format (so we could use
color), if some of you folks who do this for a living want
to jot some down for me. :-)
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438 E-Mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155
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