[Volute] r5251 - trunk/projects/time-domain/timesysnote

Volute commit messages volutecommits at g-vo.org
Tue Dec 4 09:24:18 CET 2018


Author: msdemlei
Date: Tue Dec  4 09:24:17 2018
New Revision: 5251

Log:
timesysnote: Replacing UT1 with UT, making it the label for legacy GMT.

(See http://mail.ivoa.net/pipermail/apps/2018-November/001314.html for the
rationale)

Modified:
   trunk/projects/time-domain/timesysnote/timesysnote.tex

Modified: trunk/projects/time-domain/timesysnote/timesysnote.tex
==============================================================================
--- trunk/projects/time-domain/timesysnote/timesysnote.tex	Fri Nov 30 23:23:11 2018	(r5250)
+++ trunk/projects/time-domain/timesysnote/timesysnote.tex	Tue Dec  4 09:24:17 2018	(r5251)
@@ -2,6 +2,12 @@
 \usepackage{todonotes}
 \input tthdefs
 
+\newenvironment{widedescription}[1][0pt]
+  {\list{}{\labelwidth=0pt \addtolength{\leftmargin}{-0.5cm}%
+    \addtolength{\rightmargin}{-0.5cm}%
+   \let\makelabel\descriptionlabel}}
+  {\endlist}
+
 \lstloadlanguages{XML}
 \lstset{flexiblecolumns=true,tagstyle=\ttfamily,
 showstringspaces=False,basicstyle=\footnotesize}
@@ -136,7 +142,9 @@
 \section{A TIMESYS Element}
 
 \begin{table}[th]
-\begin{description}
+\begin{widedescription}
+\addtolength{\leftmargin}{2cm}
+\addtolength{\itemindent}{-1cm}
 \item[TAI] (International Atomic Time) atomic time standard, ${\rm TT}-
 \rm{TAI} = 32.184 {\rm s}$.
 \item[TT] (Terrestrial Time; IAU standard) time measured by a
@@ -145,11 +153,12 @@
 an empirically determined factor $L_C$.  It is continuous with the
 ephemeris time ET widely used before 1984-01-01; in TIMESYS, the term TT
 should therefore be used for times in ET, too.
-\item[UT1] Earth rotation time
+\item[UT] Earth rotation time. We do not distinguish between UT0, UT1,
+and UT2; applications requiring this level of precision need additional
+metadata.  This should also be used to label GMT times in datasets covering 
+dates before 1972-01-01.
 \item[UTC] (Universal Time, Coordinated) this is TAI, with leap seconds
 inserted occasionally in order to keep UTC within 0.9 s of UT1.
-This should also be used to label GMT times in datasets covering 
-dates before 1972-01-01 (altough GMT was defined fairly differently).
 \item[GPS] (Global Positioning System) runs (approximately) synchronously with
 TAI
 \item[TCG] (Geocentric Coordinate Time) time measured by a clock moving
@@ -167,7 +176,7 @@
 \item[UNKNOWN] This value indicates clients cannot transform the times
 reliably; this is to be used for simulated data, free-running clocks,
 or data for which information on the time scale has been lost.
-\end{description}
+\end{widedescription}
 \caption{The initial list of defined time scales, evolved from the STC 1
 data model \citep{2007ivoa.spec.1030R}.  In a vocabulary, the
 descriptions should contain normative references.}
@@ -176,7 +185,7 @@
 
 
 \begin{table}[th]
-\begin{description}
+\begin{widedescription}
 \item[TOPOCENTER] The location of the instrument that made the observation
 \item[GEOCENTER] The center of the earth
 \item[BARYCENTER] The barycenter of the solar system
@@ -185,7 +194,7 @@
 \item[UNKNOWN] The times cannot be transformed to a different reference
 position reliably.  This is to be used for simulated data or for data
 for which the reference position has been lost.
-\end{description}
+\end{widedescription}
 
 \caption{The initial list of defined reference positions, evolved from the STC 1
 data model \citep{2007ivoa.spec.1030R}.  In a vocabulary, the


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