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Re: vectors on maps [message #13594 is a reply to message #13588]

Wed, 25 November 1998 00:00

wmc
Messages: 117
Registered: February 1995

Senior Member

Varavut Limpasuvan <var@atmos.washington.edu> writes:
> Is it possible to overlay vectors (say wind vectors) on a stereographic
> (or any other type) projection map? I dont think "velovect" works for
> this situation. Help.

Drawing arrows (vectors) is always a pain... for polar stereos, the transformation
is fairly easy though: if (fx,fy) are your vectors in (lo,la) directions, then
fx1= fx*cosd(lo)+fy*sind(la)
fy1=-fx*sind(lo)+fy*cosd(lo)
are the rotated vectors. Remember you need to use convert_coord to draw everything
in device space or you'll regret it.

For a general map projection, the transformation is harder. I would guess that you
would have to define a scale length for your vectors, definte their ends in lat-lon
coords, and use convert_coord to "rotate" them.

- William

---
William M Connolley | wmc@bas.ac.uk | http://www.nbs.ac.uk/public/icd/wmc/
Climate Modeller, British Antarctic Survey | Disclaimer: I speak for myself

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[Message index]

		Re: vectors on maps By: Varavut Limpasuvan on Wed, 25 November 1998 00:00
		Re: vectors on maps By: mirko_vukovic on Wed, 25 November 1998 00:00
		Re: vectors on maps By: hcp on Wed, 25 November 1998 00:00
		Re: vectors on maps By: wmc on Wed, 25 November 1998 00:00

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