[ncl-talk] Fwd: Pennants wind barbs thickness

Kyle Griffin ksgriffin2 at wisc.edu
Thu Jul 24 13:13:49 MDT 2014

As Dave is one of the developers, he does usually know best. However, if it
is very important to you to change it and you have a reasonable number on
your plot, I would recommend outputting your file as a PS, EPS, or PDF and
taking the vector file into a post-processing program such as Adobe
Illustrator or similar. There, you can edit the length/width/color/position
of the lines as necessary. Beyond that, I doubt this feature is simple to
address. If you were going to set about fixing this as a user, you could
start writing the code to draw each line individually relative to a base
point and use the gsn_add_polyline(...) function or similar to try and
construct these on your own. For the pennants, you would likely need
gsn_add_polygon(...) to create a filled polygon, once again rotated to the
angle of each wind barb line. Of course, this would be duplicating much of
the code already written behind-the-scenes in NCL, but it IS possible if
you really need a customized implementation in the immediate future.


Kyle S. Griffin
Department of Atmospheric and Oceanic Sciences
University of Wisconsin - Madison
Room 1421
1225 W Dayton St, Madison, WI 53706
Email: ksgriffin2 at wisc.edu

On Thu, Jul 24, 2014 at 1:50 PM, Rabah Hachelaf <hachelaf at sca.uqam.ca>

> Hi David,
> Yes i re-post my question maybe some one from NCL users has an other idea.
> Rabah
> 2014-07-24 14:11 GMT-04:00 David Brown <dbrown at ucar.edu>:
> Hi Rabah,
>> As you know I previously answered this question for you personally prior
>> to your joining ncl-talk. For the record I am now answering on ncl-talk:
>> You have diagnosed the problem correctly, and unfortunately there is no
>> resource to directly control the size of the pennant part of the wind barb
>> glyphs. The size and area of the pennants is fully determined by
>> the vcWindBarbTickLengthF and the vcWindBarbTickAngleF. Unfortunately there
>> is currently no adjustment made to account for the width of the lines,
>> which also has the effect of making the barbs longer than their nominal
>> length. No one has ever asked for this kind of flexibility in the past, but
>> I can see that it could be useful.
>> You could try playing with the tick length and tick angle resources. They
>> may help give you a combination that looks better. But until we can add
>> another option, my suggestion would be to just try to keep the width as
>> small as feasible for your purposes.
>>  -dave
>> On Tue, Jul 22, 2014 at 4:54 PM, Rabah Hachelaf <hachelaf at sca.uqam.ca>
>> wrote:
>>> Hi NCL users,
>>> I have problem with plotting wind barb with a relatively big thickness
>>> I am using vcWindBarbLineThicknessF command to increase wind barb
>>> thickness
>>> it's correct for all wind barbs only for higher than 50KT ones where the
>>> pennants or small triangle aren't affected by the thickness set.
>>> When reading some documentation i noted that
>>>   " The pennants are drawn using a filled polygon, while the ticks, the
>>> shaft, and the calm circle are all rendered with polylines."
>>> So i think this is why pennants aren't affected by the thickness change.
>>> Have you some tricks to solve this problem and get the same pennants
>>> thickness like the ticks.
>>> Attached you can find an example of my case, where wind speed is
>>> supposed to be about between 55KT and 60KT
>>> Thank you.
>>> ------------------------------
>>> Cordialement,
>>> Best regards,
>>> Rabah Hachelaf
>>> Msc Studient UQAM
>>> Montréal/CANADA
>>>      ____
>>>     (       )
>>>    (        )
>>>   (___ __)
>>>    /////////
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> --
> ------------------------------
> Cordialement,
> Best regards,
> Rabah Hachelaf
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> ncl-talk mailing list
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