Re: Horrible map reprojections

["Liam E. Gumley" <Liam.Gumley(at)ssec.wisc.edu>]

Ben Marriage wrote:
> 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).

I prefer to use the MAP_SET keyword SCALE to create map projections
which fill a window:

window, /free, xsize=1000, ysize=300
map_set, 0, 180, xmargin=0, ymargin=0, scale=165e6, /mercator
map_continents
map_grid, /label

> 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.

It might be an artifact of the projection. Try it again using the
projection I suggest above.

Cheers,
Liam.
http://cimss.ssec.wisc.edu/~gumley