Re: Contour plots on maps

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

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

> I have been trying to plot some contour maps onto different map
> projections, and for the most part, it is working. I have been having
> some troubles, however...
> 
> Sometimes, contours try to connect across the map, cutting diagonally
> across other lines, instead of terminating at the edges. These lines are
> not at the borders of the data, merely at the borders of the current
> projection.
> 
> I have also had troubles with filled contours on map projections
> (Mercator, in my case). While filled plots look nice with no map
> projection used, with Mercator they are overwritten with white blocks at
> times, leaving only a few spots of colour.  The help says that using map
> projections can cause filled contour troubles... Are there any
> workarounds?

There are several articles that you will really want to 
read on my web page, but I would start with this one,
because you definitely have "holes" in your contour plots:

   http://www.dfanning.com/tips/contour_hole.html

The other problems can probably be solved by always
specifying the center of the map projection with Map_Set.
Here is another article that deals with an image instead
of a contour plot on a map projection, but the idea is 
the same:

   http:/www.dfanning.com/tips/map_image.html

Cheers,

David

P.S. Welcome to the club. You should be receiving
your Welcome Packet in the mail real soon now. :-)

-- 
David Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438 E-Mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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