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Re: day or night [message #82636]

Thu, 27 December 2012 08:06

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Gompie writes:

> I have more than 62000 points that are spread over different seasons and lat lons ,on which I have to apply the day/night test.
>
> Is it possible to map the lat lon onto the image coordinates of the image output of cgterminator or sunclock and get a number telling me if it is day or night at that point.
>
> PS:
> sunclock routine in the link you gave ( http://fermi.jhuapl.edu/s1r/idl/s1rlib/local_idl.html) looks promising if takes care of seasonal variations.
>
> If I use cgterminator, due to its problem with flip, I have visually inspect each of the 62000 points so practically not possible unless you give a way out.

Well, if there is a way out, you aren't going to get it
from me. I'm spending the day with the family celebrating
a late Christmas. I'm just say that IF there is an
answer, it will probably be found among the JHUAPL
time routines.

It is certainly possible to map lat/lon positions to
image coordinates. I find Value_Locate, used in conjunction
with projected XY values, to be invaluable for this purpose.

Cheers,

David

--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")

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[Message index]

		Re: day or night By: David Fanning on Thu, 27 December 2012 08:06
		Re: day or night By: Gompie on Thu, 27 December 2012 04:03
		Re: day or night By: David Fanning on Wed, 26 December 2012 22:52
		Re: day or night By: David Fanning on Wed, 26 December 2012 22:21

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