Re: Visad and Maps

Hi Fábio,

> I'm working with Cicero and we are stucked with this difficulty to plot
> maps using the Visad library. The fact is that we don't want to reinvent
> the wheel and I've told him to ask people who already had the same
> problem about their solutions.
> . . .

In VisAD we represent maps as UnionSets of Gridded2DSets
with manifold dimension = 1. There is a simple example in
visad/examples/ You can also look at the getData()
method of visad/data/mcidas/ to see our
code for reading McIDAS map files and constructing UnionSets.

As I suggested to Cicero, you should try to print out the
number of Gridded2DSets in your UnionSet. If there are a
large number of small Gridded2DSets (for example, if each
contains just one line between a pair of points), then you
need to find a way to combine them into fewer Gridded2DSets
with more points each. This should be possible for map
boundaries and rivers.

We use this approach with the McIDAS map files and get good
performance. I think Unidata does the same thing with Shape
files containing maps.

Good luck,
Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI  53706
hibbard@xxxxxxxxxxxxxxxxx  608-263-4427  fax: 608-263-6738

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