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Re: Direction of Wind Vectors: A bug? [message #90289 is a reply to message #90288]

Wed, 18 February 2015 11:44

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

wlandsman writes:

>
> On Wednesday, February 18, 2015 at 1:32:50 PM UTC-5, David Fanning wrote:
>
>> So, here is my question. Are both of these programs "right"? If not, why
>> not? And, which would convey the "true wind direction" more convincingly
>> on a plot?
>
> I'd vote for the partvelvec.pro approach where the angle -- like everything else on the map -- is distorted by the unequal projections.
>
> However, in a similar case I chose the opposite approach -- in my tvcircle.pro I have the comment
>
> "TVCIRCLE always draws a circle --- even when in data coordinates and the X and Y data scales are unequal. (The X data scale is used to define the circle radius.) If this is not the behavior
> you want, then use TVELLIPSE instead."
>
>
> In any case, the behavior of the program should be documented (which partvelvec.pro currently isn't), and perhaps a keyword could be added to let the user choose which approach he wants.

I'm having a hard time wrapping my head around whether both approaches
are "right", or are they both "wrong." Or, maybe there is some other
combination. It would be easier (and maybe the right approach) to draw a
"stream line" instead of a vector. Then, at least you could visually see
the distortion.

In any case, I can't quite see where I would introduce the actions of
the proposed keyword. And, then, adding a real map projection is just...
Whew! I need another bottle of Tylenol. :-(

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")

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[Message index]

		Direction of Wind Vectors: A bug? By: David Fanning on Wed, 18 February 2015 10:32
		Re: Direction of Wind Vectors: A bug? By: wlandsman on Wed, 18 February 2015 11:23
		Re: Direction of Wind Vectors: A bug? By: David Fanning on Wed, 18 February 2015 11:44
		Re: Direction of Wind Vectors: A bug? By: natha on Wed, 18 February 2015 12:04
		Re: Direction of Wind Vectors: A bug? By: David Fanning on Wed, 18 February 2015 12:09
		Re: Direction of Wind Vectors: A bug? By: Paul Van Delst[1] on Wed, 18 February 2015 12:25
		Re: Direction of Wind Vectors: A bug? By: David Fanning on Wed, 18 February 2015 12:46
		Re: Direction of Wind Vectors: A bug? By: David Fanning on Wed, 18 February 2015 14:23
		Re: Direction of Wind Vectors: A bug? By: Fabzi on Wed, 18 February 2015 14:27
		Re: Direction of Wind Vectors: A bug? By: David Fanning on Wed, 18 February 2015 14:44
		Re: Direction of Wind Vectors: A bug? By: David Fanning on Mon, 23 February 2015 07:28

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