> For T&E it really matters see NASA's Mars Climate Orbiter and the need for heroics in the Gimli glider.

> You need to keep to the same unit.

Completely agreed. You’ll get similar issues if you have one set of parts using m/s and others using km/hr.

And you’ll avoid those issues with any standard, whether it’s m/s, knots or mph. The important thing is to have a standard.