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Re: Time Woes [message #30547 is a reply to message #30471]

Thu, 02 May 2002 15:26

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

David Fanning <david@dfanning.com> writes:
>
> Here is what I know. I have some TRMM data in a particular
> lat/lon range at a particular time (e.g. 4AM on 7 July 2001).
> I want to pull out any QSCAT wind data that might overlap my
> TRMM data by about an hour or two.
>
> What questions would it be helpful for me to know to ask?

Hey David--

Everybody is bothering you about TAI, UTC, leap seconds, you must be
going crazy! If you are just interested in precisions of overlaps of
"an hour or so" then you really don't care about leap seconds, so you
can probably forget about most of it. (just wait until you get to TT,
TDT, TDB, TCG and TCB!)

For doing overlaps the real necessity is to get the times of your TRMM
data and QSCAT data into the same format, doesn't matter what format
that is. One easy one is to use Julian days as Ben, et al have been
describing. You have a "seconds-since-epoch" format, so you would
indeed take:

t_trmm = .... ;; Seconds since 1980
;; Convert to Julian days (86400 seconds per day)
jd_trmm = julday(0,1,1980, 0,0,0) + t_trmm/86400

and then you probably have to do something similar to the QuikScat
times, right?

Craig

--
------------------------------------------------------------ --------------
Craig B. Markwardt, Ph.D. EMAIL: craigmnet@cow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
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[Message index]

		Time Woes By: David Fanning on Wed, 01 May 2002 12:41
		Re: Time Woes By: Craig Markwardt on Thu, 02 May 2002 15:26
		Re: Time Woes By: thompson on Thu, 02 May 2002 14:51
		Re: Time Woes By: btupper on Thu, 09 May 2002 07:21
		CDF_EPOCH (was Re: Time Woes) By: Brian Jackel on Thu, 02 May 2002 12:05
		Re: Time Woes By: Struan Gray on Thu, 02 May 2002 08:34
		Re: Time Woes By: David Fanning on Thu, 02 May 2002 06:38
		Re: Time Woes By: btupper on Thu, 02 May 2002 06:11
		Re: Time Woes By: Ken Mankoff on Thu, 02 May 2002 06:07
		Re: Time Woes By: Paul Van Delst[1] on Wed, 01 May 2002 14:24
		Re: Time Woes By: David Fanning on Wed, 01 May 2002 14:00
		Re: Time Woes By: Robert Stockwell on Mon, 06 May 2002 06:14
		Re: Time Woes By: Ken Mankoff on Wed, 01 May 2002 13:10

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