Re: [ferret_users] Plotting curvilinear vectors

["E. D. (Ned) Cokelet" <Edward.D.Cokelet@xxxxxxxx>]

I think that the Ferret vectors are wrong because they were written with the idea that the entire vector - tail location, shaft length, arrow head and direction - should be transformed in your coordinate transformation.  That is invalid.  The only thing the should be mapped is the tail locations.  The shaft length and  arrowhead should not be transformed.  That leaves the direction which is a bit trickier.  I wrote a journal script that Ansley has made available to the community called poly_vector.jnl.   It works with the various Ferret map projections, e.g. Mercator, etc, gets the directions right and lets you scale the vector lengths.  If you can use one of those for your curvilinear mapping, or make up a new mapping transform that follows their style, then you should be able to map vectors correctly with the new script.  Billy Kessler has modified this a bit to give better arrowheads when the arrows get really short.  I am not sure if that is implemented community-wide yet.

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Edward D. (Ned) Cokelet, Ph.D. Oceanographer

NOAA/PMEL off:  (206) 526-6820

7600 Sand Point Way NE fax: (206) 526-6485

Seattle, WA 98115-6439

Edward.D.Cokelet@noaa.gov

The contents of this message are mine personally and do not necessarily reflect any position of the Government or the National Oceanic and Atmospheric Administration.