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Re: Day/Night Terminator on Map Projection [message #48366 is a reply to message #48311]

Wed, 12 April 2006 23:00

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

David Fanning writes:

> Does anyone have IDL code for calculating the day/night
> terminator on a map projection? Or perhaps an example of
> a map in which you have done this?

Thanks to Kelly Dean and Andrew Cool for suppling me
with a few (slightly buggy!) examples of how to do this. :-)

After spending most of the day scratching my head and
pondering yet again the shear beauty of Ray Sterner's
JHUAPL code, I finally came up with something I like.

Rather than just drawing the day/night terminator, I wanted
to see it in living color. So I used the AVHRR data set that
comes in the IDL demo directory for this purpose. It makes
a very pretty map, if I do say so myself!

You can see the code I came up with and a nice picture
here:

http://www.dfanning.com/map_tips/terminator.html

To run the code, you will need to have both the Coyote
Library and the JHUAPL Library on your IDL path.

I'll probably spend some time tomorrow making a little
stand-alone application out of this with widgets so you
can change the time interactively. It's more interesting
than I would have thought to change the time and watch
the sun and shadows move though the day and year. :-)

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/

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[Message index]

		Day/Night Terminator on Map Projection By: David Fanning on Fri, 07 April 2006 17:26
		Re: Day/Night Terminator on Map Projection By: JD Smith on Thu, 13 April 2006 16:15
		Re: Day/Night Terminator on Map Projection By: David Fanning on Thu, 13 April 2006 08:20
		Re: Day/Night Terminator on Map Projection By: Haje Korth on Thu, 13 April 2006 05:10
		Re: Day/Night Terminator on Map Projection By: David Fanning on Wed, 12 April 2006 23:00

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