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[CSS21] 4.3.2 Lengths (reference pixel?)

From: Dr. Olaf Hoffmann <Dr.O.Hoffmann@gmx.de>
Date: Thu, 9 Dec 2010 18:31:50 +0100
To: www-style@w3.org
Message-Id: <201012091831.50783.Dr.O.Hoffmann@gmx.de>
Hello,

as far as I understand this, after the changes, 
the sections about the reference pixel are misleading.

It is defined now:
"
in: inches — 1in is equal to 2.54cm.
cm: centimeters
mm: millimeters
pt: points — the points used by CSS are equal to 1/72nd of 1in. 
pc: picas — 1pc is equal to 12pt.
px: pixel units — 1px is equal to 0.75pt.
"
And because the size of a mm or cm is precisely known by measurements
of a second and the defintion of the speed of light,
a px results in (127/480) mm.
A standard unit like a second (and therefore derived units like
meter, mm, cm etc) are of high cultural and scientific importance
and it is as well important for techniques and trade to be able to
rely on the assumption, that all people follow the same definition
of such international standard units (to avoid catastrophes and
cheating). Therefore there cannot be another definition for 
international standard units. 
(It is of course possible to propose a high precision method and
measurement of 1s to improve the current definition, but this does
not happen here obviously).


Therefore the section about the reference pixel and the image
about it is misleading now or in contradiction with the new definition
above, because there can be only one definition of a px.
I propose to remove this part about the reference pixel therefore.

Olaf
Received on Thursday, 9 December 2010 17:32:31 GMT

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