Re: [Matplotlib-users] Projection Direction Distortion

[Jody K. <jk...@uv...>]

Hi Mat,

On Apr 26, 2013, at  3:03 AM, Mathew Topper <mat...@ed...> wrote:

> I have a set of wave directions in lon lat,

Not clear how a direction is given as a lon lat.  Do you mean you have a set of vectors, each defined as lon/lat pairs?   

> but I want to display them 
> in a UTM type projection. I believe the directions will be distorted, 
> but I'm not sure by how much.

It depends on what you want - if you want the arrow to point where the wind would go after X minutes, then you want the "distortion".  If you want the viewer to be able to pick off the geographic heading by eye, then simply convert your lon lat pairs to heading/length pairs and plot them in the axis frame.  See http://matplotlib.org/basemap/users/mapcoords.html for how to convert from basemap to the underlying axis frame.

In an ideal world your projection would not be over such a large area that any of this matters - if your vector is off by 1 degree, who will be able to tell in a plot? 

Cheers,    Jody

--
Jody Klymak    
http://web.uvic.ca/~jklymak/