| Re: Filled Contour Colors on Maps Incorrect [message #26812 is a reply to message #26811] |
Wed, 26 September 2001 03:52  |
Martin Downing
Messages: 136
Registered: September 1998
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Senior Member |
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"David Fanning" <david@dfanning.com> wrote in message
news:MPG.161af29e35a9e8be9896c8@news.frii.com...
> Folks,
>
> I have a feeling you map guys are not going to like this
> post. :-(
>
> Here is a filled-contour-on-a-map-projection problem
> that has been giving me nightmares.
>
> I wish to put a filled contour plot on a cylindrical
> map projection. I've read all the articles on that
> Coyote site about filled contours and I am aware of
> all the pitfalls. I have created my own contour intervals,
> and I know exactly which colors I am using for my
> filled contours.
>
> I follow the recommended procedure. I create a map
> projection with Map_Set. I add the filled contour
> command by specifying the data and the vectors of
> latitude and longitude and I use the Contour command
> with the OVERPLOT keyword set. But...
>
> The colors are not right. I know this for two reasons.
> First, I have used exactly the same data set with the
> GrADS software and produced a contour plot that has the
> same contour intervals, but is colored differently.
> Second, I have confirmed that the data is identical
> in both the GrADS and IDL programs.
>
Hi David,
The CONTOUR bug can be illustrated very well in your code by just switching
off /FILL in the first contour call, or trying this to illustrate it:
Map_Set, 0, 180, /CYLINDRICAL, LIMIT=limit, $
Position=[0.1,0.15,0.9,0.9], $
Color=white, charsize=2
; edited first call with FILL unset
Contour, data, lons, lats, $
C_Colors=cn, Color=WHITE, $black, $
Max_Value=cmax, Min_Value=cmin, $
Levels=clevels, /OVERPLOT
wait , 5 ; Time to see that the unfilled contours make sense
; now do the original call:
Contour, data, lons, lats, $
C_Colors=cn, Color=WHITE, $black, $
Max_Value=cmax, Min_Value=cmin, $
Levels=clevels, /FILL, /OVERPLOT
; Oh dear - the filled contours have has no relation to the unfilled
contours
cheers
Martin
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