My favourite was a sign on Goat Island (US side of Niagara Falls) which
gave the flow rate as 75000 gal (283906 L) per second. I haven't been
there since the redevelopment of Goat Island started so I don't know if
it is still there.
Stan Jakuba wrote:
My comment - I stand by my expressing measurements that warrant barely
two
significant digits with no more digits than that. In the world of
energy and power and the (ever changing) cost, two sigificant digits
is enough for such statistical data. Particularly if they are intended
for public understanding and memory-retaining, such as my table.
If you look at the EIA (Energy Information Administration) tables, you
see numbers
like 56.59 tons of CO2, 1,589.9 Billion Kilowatthours (sic), 1,364,697
million cubic feet. As another example, all liquid hydrocarbons contain
between 46 MJ/kg and 48 MJ/kg. Where 47 would obviously suffice for these
statistical purposes, there is 46.046, 46.871, etc., a far greater
precision
that there is the difference in the HHV from one shipment of the same
stuff
to another. And if you think that this (1 acre = 4046.86 m² or 4046.87
m²)
is worth considering in the daily life, look at your deed; it says you
own X
ft² "more or less".
This excess of significant digits probably leads to similarly ridiculous
numbers in information published by those who use EIA data. I wrote to
EIA a
few times about the use of SI units and this digits pollution, but
never got
any replay on any subject. The only explanation I came up with - why
anyone
would use 7 digits precision in numbers that have accuracy +/-10 % or
worse - is that their computers are programmed to sum up to 100 % with 7
significant digits. Or, as an example, the data collectors simply add
numbers from a kW producer with that of a GW producer not realizing
that kW
is far less that the error in the GW number. Also, EIA as all American
agencies endlessly convert and thus even a common-sense-rounded number in
kWh becomes an overly precise number in Btu, kJ, MJ, etc., and vice
versa.
SI prefixes allow us to express almost any value with just 3 digits.
Let's
practice that advantage wherever appropriate. Unless you are a metrology
scientist or a banker, "appropriate" is most of the time.
Stan J.
