Re: [ferret_users] vector/aspect question

["William S. Kessler" <William.S.Kessler@xxxxxxxx>]

Hi Jozef -

As a general rule, I never use vector/asp, because it distorts the  
true direction of the vectors.

Without the /asp qualifier, a vector pointing northeast in fact  
represents a wind towards the northeast. With /asp, it might not. For  
example, suppose you are plotting a region that is truly square (say  
5S-5N, 55W-45W), but set the window aspect ratio to be rectangular  
(for example like the default window). In this case, the plot will be  
stretched in the E-W direction (i.e., a map of the coastline will be  
distorted). If you plot vectors with /asp, the vectors will be  
comparably distorted, which I think is misleading. If you plot  
vectors without /asp, then the vectors will all have their correct  
directions; however, vectors that are in reality parallel to the  
coast will not appear to be. The lesson here is to always make maps  
of vectors in a viewport with the correct aspect ratio!

! in the example above:
set win/asp=`55-45/10`:axis

The main exception I would make to the above is in plotting vectors  
where the aspect ratio is necessarily distorted, like vertical sections.

Billy K

On Mar 27, 2006, at 12:16 AM, Jozef.Syktus@nrm.qld.gov.au wrote:

> Hi,
>     I am plotting winds at 850 hPa u,v using vector from GCM model  
> output, the data is in lat long coordinates (T63). Should I use  
> vector/aspect option or just vector?
>
> Regards,
>
>
>
> Jozef Syktus
>
> Climate Impacts and Natural Resource Systems
> Department of Natural Resources, Mines and Water
> 80 Meiers Rd., Indooroopilly Qld 4068 Australia
>
>
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