How to control the streamline?

[Andreas Schneider]

On Wed, Aug 12, 2009 at 2:38 PM, Jennifer Adams<jma at cola.iges.org> wrote:
> There are no specific controls for the arrows in the streamlines. I'll put
> it on my list of requested features.

I have a patch for gxstrm.c (almost a complete rewrite). It includes
support for arrowhead size and changes strmden behavior to be less
dependent on data density and geographic location.

Its main purpose is to fix the erroneous streamlines. In current GrADS
they are generally wrong, especially near the poles, because they
assume square grid boxes everywhere. With the patch, streamlines
become usable with the nps and sps projections.

The patch includes performance optimizations, but may actually run
slower because of higher precision and a more sophisticated algorithm.

The patch is based on 2.0.a2. I planned to do more code clean-up,
tests and maybe more enhancements (good default density for all map
projections and all locations, nicer positions for arrow heads, ...),
but didn't find time to actually do it. I ran the patched a2 for a
year without problems (but I generate similar maps most time).

The attached version of the patch is adapted to 2.0.a7.1, but I don't
even know if it compiles, because the GrADS build system isn't easy
and I got errors at bootstrap that weren't resolvable for now.

Andreas
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