In response to someone talking about deprecation of the hectare, I would like to
clarify some
matters. The SI book lists the litre (l, L) and tonne (t) as non-SI units accepted for
use with
the SI, that is to say, the BIPM has no intent to deprecate them.
As 1 L = 1 dm3 and 1 mL= 1 cm3 (no cc or c.c.), I consider when using symbols,
dm3 and cm3
are preferred to L and mL, though the litre may be used as a special and shorter name
of the cubic
decimetre.
1 t = 1000 kg = 1 000 000 g = 1 Mg. Megagrams are rarely used, and I consider it
more
convenient to use the tonne for large mass. US NIST SP 811 states multiples of the
tonne or metric
ton may be used, such as kt for kilometric ton, but I prefer kilotonne or kiloton of
metric. In no
event should the SI prefixes be used with long or short tons which belong to WOMBAT
and the like,
such as kiloton of long or short.
The SI book lists the are (a) and hectare (ha) as non-SI units currently accepted
for use
with the SI, i.e., the BIPM has intent to deprecate them but exact time to do so may
be unknown
yet. 1 a = 1 dam2 and 1 ha = 1 hm2. Again, I consider when using symbols, dam2 and hm2
are
preferred to a and ha, though the are and hectare may be used as special and shorter
names of the
square decametre and square hectometre.
In the People's Republic of China, the symbol ha is not to be used. See also the
note 5 in my
SI Units and Prefixes: English-Chinese at http://www.geocities.com/jusjih/si-zh.html#5
. This page
of mine serves as a "maintenance page" of J. R. Frysinger's SI in Chinese at
http://www.cofc.edu/~frysingj/SI_chinese.htm since I update my pages very frequently
that he
cannot always catch on. I am still in the process of reconfiguring my maintenance page.
Justin
=====
Justin JIH http://www.geocities.com/jusjih/
World-Wide Anti-Conscription Unity in Yahoo! Groups:
http://groups.yahoo.com/group/anti-conscription
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