[gradsusr] Plot vector - geographic X trigonometric system

[Gabriel - ud Carvalho]

Jeff, tanks a lot! It worked OK!


2010/9/27 Jeffrey Duda <jdduda at iastate.edu>

> Oh ok.  I get it now.  yeah, I've run into this problem myself.  Try using
>
> u = wind_magnitude * cos(450 - degrees_in_your_data)
> v = wind_magnitude * sin(450 - degrees_in_your_data)
>
> Jeff
>
>
> On Mon, Sep 27, 2010 at 2:26 PM, Gabriel - ud Carvalho <
> gabriel.ud at gmail.com> wrote:
>
>> I think that I was not clear,
>> I can´t do this suggestion because the 'sin' function is oriented to the
>> trigonometric system, which isn´t the system in which my data is oriented.
>> For instance, in my data, a 270 degrees is equivalent to 180 degrees in the
>> trigonometric system.
>>
>> I hope I am more clear now, even thoug the roughness of my english...:)
>>
>> Thanks in advance,
>> Gabriel  Carvalho
>>
>> 2010/9/27 Jeffrey Duda <jdduda at iastate.edu>
>>
>>> Gabriel,
>>> As long as your data contains wind direction oriented such that 0 deg in
>>> your data refers to a wind blowing to the north (or from the south), then
>>> your components can be broken down as:
>>>
>>> u = wind_magnitude * sin(direction)
>>> v = wind_magnitude * cos(direction)
>>>
>>> Of course, when actually putting these computations into Grads you will
>>> want to change "direction" from degrees to radians.
>>>
>>> Jeff Duda
>>>
>>>  On Mon, Sep 27, 2010 at 12:34 PM, Gabriel - ud Carvalho <
>>> gabriel.ud at gmail.com> wrote:
>>>
>>>>  Hello you all!
>>>> Here is the deal:
>>>> In my data, the wind direction is in degrees, with a geographic
>>>> representation (wich means that 0 is at the north and goes clockwise),
>>>> the problem is that to display this data with 'gxout vector', I have to
>>>> decompose it in 'u' and 'v'. In order to do this, I have to use the
>>>> trigonometric functions 'sin' and 'cosin'. The problem is here, these
>>>> functions assume that the input data is with a trigonometric representation
>>>> (wich means that 0 degrees is eastside and goes anti-clockwise),butthey
>>>> aren´t, so, it got all messed up.
>>>>
>>>> I don´t know what to do,but I believe that this is a common problem,
>>>> I hope someone will know the answer...
>>>>
>>>> Sorry about my poor english,
>>>>
>>>> My best regards,
>>>> Gabriel Carvalho
>>>>
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> gradsusr mailing list
>>>> gradsusr at gradsusr.org
>>>> http://gradsusr.org/mailman/listinfo/gradsusr
>>>>
>>>>
>>>
>>>
>>> --
>>> Jeff Duda
>>> Iowa State University
>>> Meteorology Graduate Student
>>> 3134 Agronomy Hall
>>> www.meteor.iastate.edu/~jdduda <http://www.meteor.iastate.edu/%7Ejdduda>
>>>
>>> _______________________________________________
>>> gradsusr mailing list
>>> gradsusr at gradsusr.org
>>> http://gradsusr.org/mailman/listinfo/gradsusr
>>>
>>>
>>
>> _______________________________________________
>> gradsusr mailing list
>> gradsusr at gradsusr.org
>> http://gradsusr.org/mailman/listinfo/gradsusr
>>
>>
>
>
> --
> Jeff Duda
> Iowa State University
> Meteorology Graduate Student
> 3134 Agronomy Hall
> www.meteor.iastate.edu/~jdduda
>
> _______________________________________________
> gradsusr mailing list
> gradsusr at gradsusr.org
> http://gradsusr.org/mailman/listinfo/gradsusr
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://gradsusr.org/pipermail/gradsusr/attachments/20101006/bef54579/attachment-0003.html