Subject: OGIP/93-001 - OGIP memo on the standard strings for physical units

From: [email-masked] (Ian M George, Code 668, NASA/GSFC, USA (Usque ad mortem bibendum))
Date: Wed, 14 Apr 93 20:20:18 -0400

FITS gurus

... Lorella & I have put together a list of standard strings & rules we 
would like to see adopted OGIP-wide regarding the specification of physical
units within FITS files. These have been written up as a [draft] OGIP memo 
(# OGIP/93-001), and copies circulated to:
	- a number of OGIP people in Bldg 2 directly
	- Don Jennings via GSFC internal mail (3 copies for CGRO SSC)
	- Barry Schlesinger via GSFC internal mail
If you have not (or are not about to get) copies, but would like one, 
please see/e-mail me.

.. During it's construction we were primarily thing about TUNITnnn keyword 
values, but there is no reason why the same strings can't be used elsewhere if 
necessary. We welcome all comments, suggestions & additions excluding those 
bemoaning the passing of imperial & c.g.s. units (after much debate, we 
decided that it was easiest [& most consistent] mainly to adopt the 
recommendations of the IAU).

Ian M George
HEASARC

PS: Yes, thank you, we already know of most of the typos...

NOTE ADDED IN PROOF
-------------------
Since I photocopied & distributed the current draft, Bill Pence has made 
the very valid point that if we change the string for the (little used)
unit of siemens from "S" to "siemens" (Table 1), then there is no 
case sensitivity amongst the currently listed strings. Since this has 
obvious s/w advantages, I fully support this, and the draft should be 
considered to have been ammended so.

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From: [email-masked] (Don Wells)
Date: Wed, 14 Apr 93 21:10:34 -0400

Usque ad mortem bibendum writes:
 > ... have.. list.. of standard.. physical units within FITS files..
 > [draft] OGIP memo (# OGIP/93-001).. after much debate, .. decided..
 > easiest [& most consistent] .. adopt  recommendations of the IAU..

I applaud this action, which is consistent with the FITS tradition
which Eric Greisen and I started in 1979 when we specified use of SI
units in FITS files. Please stand firm on this when the inevitable
criticism comes.  Your actions will set a good example for the rest of
the FITS community and will, in the long run, pay handsome dividends
for science.

Donald C. Wells             Associate Scientist        [email-masked]
National Radio Astronomy Observatory                   +1-804-296-0277
520 Edgemont Road                                 Fax= +1-804-296-0278
Charlottesville, Virginia 22903-2475 USA            78:31.1W, 38:02.2N

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From: [email-masked] (Lee E. Brotzman)
Date: Thu, 15 Apr 93 10:06:18 -0400

> (# OGIP/93-001), and copies circulated to:
  ...
> If you have not (or are not about to get) copies, but would like one, 

There wasn't an e-mail address on the signature, so I'll ask publically.
Please send me this draft.  I have published 100 astronomical catalogs in FITS
on CD-ROM and used a consistent set of units throughout, following the
guidelines in the IAU Style guide.  It would be interesting to see what you 
have come up with.  

I have also put in a proposal for ADP funds to extend the FITS formatting of
ADC catalogs to an additional 150 or so catalogs and I fully intend to use the
same unit and field name conventions I used on the CD-ROM.  The first product
(assuming of course that I get the funding) will be a data dictionary containing
all of the common TTYPE and TUNIT keyword values I plan to use.  That will be
publically available over the Internet within the first month or two of
starting work (say, late this summer).

-- 
-- Lee E. Brotzman                    Internet:  [email-masked]
-- Hughes STX                         DECNET:    NDADSA::BROTZMAN
-- NASA Goddard Space Flight Center   BITNET:    ZMLEB@GIBBS