| Re: weird contour lines [message #68482 is a reply to message #68481] |
Sat, 31 October 2009 10:00   |
Libo Wang
Messages: 6
Registered: October 2009
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Junior Member |
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On Oct 31, 12:09 pm, David Fanning <n...@dfanning.com> wrote:
> Libo Wang writes:
>> Hi, I used the following code to set up a stereographic projection map
>> and overplot NCEP pressure field on it:
>
>> MAP_SET,/stereographic, 60, -105,color=grey,limit=[30,-180,80.0,-10],/
>> continents,/isotropic
>> levels = 16
>> step=4
>> userLevels = IndGen(levels) * step + 120
>> Contour, data,lon,lat,C_Colors=black,Levels=userLevels, /overplot
>> Contour, data,lon,lat,/Overplot,
>> Levels=userLevels,c_colors=black,c_charthick=2,$
>> max_value=200,min_value=120,/Follow
>
>> However, I got weird contour lines, which you could take a look at the
>> following link:
>> http://picasaweb.google.com/libowa/DropBox?feat=directlink
>
>> Could you point out what was wrong in my codes? How could I get smooth
>> contour lines?
>
> Is this an aesthetic problem or a science problem?
>
> If it is an aesthetic problem, that NCEP data is fairly low-resolution.
> You could try CONGRIDing it to a larger size, using interpolation,
> before contouring it. Or, you could just try smoothing your data
> before you contour it.
>
> Cheers,
>
> David
>
> --
> David Fanning, Ph.D.
> Fanning Software Consulting, Inc.
> Coyote's Guide to IDL Programming:http://www.dfanning.com/
> Sepore ma de ni thui. ("Perhaps thou speakest truth.")- Hide quoted text -
>
> - Show quoted text -
Thanks, David. I've read helpful tips in your website. It is actually
a bit of both aesthetic problem and a science problem! A meteorologist
would probably tell me that my map is not what a standard pressure
field plot should look like!
I tried to expand my data from 144*37 to 1440*370 using cubic=-0.5 in
Congrid,the contour map did improved in some parts, but some parts got
worse:
http://picasaweb.google.com/lh/photo/pbT1Ftfbx0nqS9O3uw0tGg? feat=directlink
The NCEP data is low in resolution: 2.5 degree spacing. What else
could I try?
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