Re: Contour plots on maps

[davidf(at)dfanning.com (David Fanning)]

Simon de Vet (simon@mathstat.dal.ca) writes:

> 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.

The problem would appear to be your color table. I recommend
you load your color tables identically on both your display
device and in the PostScript device. I usually do something
like this. Suppose I am using 12 levels.

   LoadCT, NColors=12, Bottom=1
   contourColors = Indgen(12)+1
   Contour, z, x, y, Levels=contourLevels, C_Colors=contourColors, /Fill

Then what I see on my display is identical to what I see in
PostScript.

Cheers,

David

-- 
David Fanning, Ph.D.
Fanning Software Consulting
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