Re: Horrible map reprojections

[Martin Schultz <martin.schultz(at)dkrz.de>]

Ben Marriage wrote:
> 
> Hi all,
> 
> IDL> print,!VERSION
> { x86 linux unix 5.3 Nov 11 1999}
> 
> I'm trying to set up a particular map reprojection, and get some rather
> horrible results. Can somebody try this on their machine to see if it is
> reproducible please?
> 
> window,0,xs=1000,ys=300
> map_set,0,180,0,limit=[-30,-180,30,180],xmar=0,$
>   ymar=0,noborder=1,/grid,clip=0,/iso,/mercator
> map_continents,/hires
> 
> One effect is that the reprojection does not extend all the way to the
> right hand side of the plotting area (should be 0 deg long, instead it
> is about -10 deg long). Another problem is this produces lines cutting
> across the window (caused by the map_continents part).
> 
> This is only part of the problem, when trying to contour some data using
> a similar reprojection, I get lines cutting across the contour plot. I
> thought it might be a missing data problem, so set all missing data to
> !VALUES.F_NAN. No difference.
> 
> Has anybody else had a similar problem/solution?
> 
> Thanks,
> Ben

There are two things wrong here:

(1) make sure that the "center" longitude is at the center of your
LIMIT (or at least within and not at the border)
(2) you can get rid off the silly lines if you omit the clip=0
keyword.

The following looks ok to me (same version and platform as you have):
map_set,0,180,limit=[-30,0,30,360],xmar=0,$
   ymar=0,noborder=1,/grid,/iso,/mercator
map_continents,/hires

Cheers,
Martin


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[[ Dr. Martin Schultz   Max-Planck-Institut fuer Meteorologie    [[
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