[Tagging] Default maxspeed unit on waterways

[Pieren]

Hi,

Currently, le wiki ([1]) suggests that maxspeed has to specify the
unit "knots" when it's not km/h. But "knot" is the unit used worldwide
on waterways. Why should we add something obvious on all waterway
elements ? Could we suggest that the default unit for maxspeed on
waterways is "knot" and the default "km/h" remains for highways and
railways ?

Pieren

[1] http://wiki.openstreetmap.org/wiki/Key:maxspeed