On land we use km/hour or miles/hour but on water use knots!!
Hakan,
I sure hope you would be able to forgive me if my use of mph was offensive. I was replying to another fellow who used it and it was a remark about a speed that a website (motionbased) had used to show my speed.
I usually use knots, but have found that the majority of cat sailors who I have spoken with, usually quote mph when talking about speed on their cats. One way or the other, there will be some people who need to know how to convert.
LOVE!!! your helmet cam videos Hakan.
GARY