Mike_Peel added a comment.
In https://phabricator.wikimedia.org/T105623#1645307, @Jc3s5h wrote:
> I must take issue with thiemowmde's argument:
>
> - "At this point, this is false precision. The original value was not that
> precise. The original 1.06 feet had 2 decimal places, the last being 0.01
> feet = 0.003048 m."
>
> Suppose we do as thiemowmde suggests; when the user enters 1.06 feet in the
> user interface, with no ± character and no uncertainty specified, we store {
> amount: 1.06, unit: feet, upperBound: 1.06, lowerBound: 1.06 } We no longer
> have the user's original input; we now have a declaration that the value is
> exactly 1.06 feet. If the user had entered 1.06±0 because the user knew the
> value was exact, it would be stored exactly the same way. So if it is
> converted to meters the value becomes 0.323088±0 m.
In that case, it would make sense to round the result to 0.32m, i.e. to lose
some of the precision in the original number to handle the absence of an
uncertainty. Where the uncertainty in the first number is known, then this
uncertainty should be propagated (see
https://en.wikipedia.org/wiki/Propagation_of_uncertainty ) and the numbers
given appropriately, i.e. to 1SF of the newly calculated uncertainty (although
this is sometimes given to higher accuracy where the first significant digit in
the uncertainty is 1, e.g. 0.11 or 0.19, to permit more accurate unit
conversions in the future).
TASK DETAIL
https://phabricator.wikimedia.org/T105623
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To: Mike_Peel
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Liuxinyu970226, Snipre, Event, Ash_Crow, mgrabovsky, Micru, Denny, He7d3r,
Bene, Wikidata-bugs, Ricordisamoa, Kelson, MSGJ, Klortho, Wolfvoll, Aklapper,
aude
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