Need a hint - how to automatically draw "H" and "L" into a pressure chart

[Stefan Gofferje]

Hi,

I guess, I asked this already a couple of days ago but maybe I was not
explaining it the right way.

On my weather project, I have some pressure charts like this:

http://www.saakeskus.fi/index.php?function=showpic&chart=NORDIC-prmsl&number=100#top

What I would like to do is automatically draw "H" and "L" to the
appropiate point of the chart like here:

http://www.wetterzentrale.de/pics/Rtavn061.png

or here:

http://www2.wetter3.de/Animation_12_UTC/00_1.gif

I really have been thinking on how to do this but I have no idea.
Could anybody give me a hint on that?

Tervehdys Suomesta,
Stefan Gofferje

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