[OSM-talk] Units convention (Was: Mapping canals)

[Martin Trautmann]

> Indeed, the exact conversion is to multiply/divide by 0.3058 
> which produces 2.1336m or 2.134m if you round to the nearest 
> millimetre.
> 
> 7ft or 7' is so much simpler in this instance :-)

1 ft is EXACTLY 0.3048 m,
7 ft are EXACTLY 2.1336 m (7*12*25.4/1000)

I guess your choices are:
* 7 ft   (four digits, no direct calculations possible due to "text")
* 2.1336 (six digits, no unit "m" required, exact match)
* 2.14   (4 digits, rough conversion, may use exact back conversion by matching rounding)

Since there are many other definitions of foot, apart of this international foot (ranging from 0.25 m up to 0.3333333333333... m), I do not see a problem by rounding to two decimal digits.

AFAIK any numbers with units "ft" and "mph" will be converted to metric units.
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