Re: anyone plotting coastlines?

Hi John,

> a beginner....i'm struggling with trying to understand how to plot a
> coastline.  i have sets of points forming line segments but can't see how
> to use the visad data set types to connect the dots.  i'm sure the examples
> are there - but so far i haven't been able to find them.
> do i use the IrregularSet class?  what to i do to implement? code snippets
> welcome & appreciated.....

The program in visad/examples shows the basic
idea.  You construct a UnionSet of a collection of Gridded2DSets,
each with manifold dimension = 1.  Each of the Gridded@DSets
with manifold dimension = 1 is a sequence of points rendered as
a continuous line (assuming the RealTypes components of the
SetType are mapped to spatial DisplayRealTypes like XAxis and
YAxis).  The UnionSet is rendered as the disjoint union of these
continuous lines (i.e., the pen lifts between Gridded2DSets).

Also check out the SatDisplay program in visad/examples, which
uses the class to read McIDAS
map files (usually named OUTL*) into UnionSets.  These are overlaid
onto satellite images.

> Also, i've got a set of Quikscat wind speeds at irregular points in a
> scalar and am about to write an objective analysis class to fill in the
> holes so i can isocontour.  i see hints of grid interpolation methods but
> still find it hard to understand how to implement (i'm not that familiar
> with how the pieces fit together) - so find myself resorting to custom code
> to keep my spirits up.  suggestions welcome here too!

The easiest way to do this is to put your wind speeds into a
FlatField whose domain Set is an Irregular2DSet that defines
the locations of the wind speeds.  If you map the domain
RealTypes to spatial DisplayRealTypes and map wind speed to
Display.IsoContour, then the VisAD display logic will render
contour lines based on the irregular topology.  This will
allow you to skip the explicit objective analysis (which would
of course interpolate your wind speeds to a Gridded2DSet).  

VisAD supports contouring algorithm for both gridded and
irregular sampling topologies (and provides hooks for people
to define their own contouring algorithms).

> having fun,

Glad to hear it.  Please let me know if you have further

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

  • 2000 messages navigation, sorted by:
    1. Thread
    2. Subject
    3. Author
    4. Date
    5. ↑ Table Of Contents
  • Search the visad archives: