Windvectormap

[Muhammad Amjad]

Dear Chris,

Could you please check with the following formula:
wdir=atan2(u,v)/0.01745329 +180
The size of wind represents the wind speed. So, I don't think the dispariy
among the vectors can be removed.

Cheers,
Amjad.


On 11/9/09, Chris Hayes <c.hayes at weeronline.nl> wrote:
>
>  dear group,
>
> I need to plot the wind directions for stations with equally sized arrows.
>
> My dataset contains the direction in degrees (0-360).
>
> I use the gxout=vector map which requires a u and a v vector component
> (i.e. the vertical and horizontal vector component).
>
> u
> |      /winddir
> |    /
> |  /
> |/___ v
>
>
> I calculate u as -sin(winddir * pi/180)
> I calculate v as -cos(winddir * pi/180)
>
> resulting in the display-command    ' -8*(sin(winddir * 0.0175)) ; -8*(cos(
> winddir * 0.0175)) '
> (where 8 makes the size of the arrow, which usually represents windspeed
> but here is desired to be constant)
>
>
> The direction of the arrows looks fine.
> But some maps have only tiny arrows and some maps have only longtailed
> arrows.
> I cannot see a pattern. I have no mixed maps with tiny and large arrows.
>
> Should I change my formula, or the way I give the display command?
>
> thanks,
> Chris
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://gradsusr.org/pipermail/gradsusr/attachments/20091112/2f35897a/attachment.html