[Thread Prev][Thread Next][Index]

Re: [ferret_users] Plotting curvilinear vectors

Hello Ned,
Thank you for your response. I had a go with "poly_vector.jnl", but there is something wrong with the plot. My winds are not on a regular grid, but rather scattered, such as satellite data. I tried this:

file/var="lat,lon,u,v" fort.8 !a listing of lat,lon,u,v

go basemap x=280:310 y=20:40 5

go poly_vectors lon lat u v 10 "arrow" !randomly chose 10 for scale

polygon/overlay/noax/nolab/line plt_x_arrow,plt_y_arrow !no fill, just vectors

This appears:

*** NOTE: Ambiguous axes in 2D coordinate arrays
*** NOTE: Continuing as /COORD_AX=Y

I tried making a 2-d array of lat,lon,u,v, but I still get this message and the plot is still not right. Any suggestions? I am able to get the right plot with "plot_vectors.jnl" from Patrick Brockman, but don't know how to implement the key.


Quoting "E. D. (Ned) Cokelet" <Edward.D.Cokelet@noaa.gov>:

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.
------------------------------------------------------------------------ ------------------
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


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.


[Thread Prev][Thread Next][Index]

Dept of Commerce / NOAA / OAR / PMEL / TMAP

Contact Us | Privacy Policy | Disclaimer | Accessibility Statement