[Jared Russell]

We always use the same units and are allergic to things like encoder counts, loop counts, magic constants, etc. All public interfaces speak in terms of standard units, with the exception of open loop speed commands which are in the range [-1, 1]. All return values and arguments are named so that the units are explicit, and a common library is used for any necessary conversions.

Generally we use:
Distance = inches
Time = seconds
Angles = degrees (in yaw 0 degrees is robot forward, increasing clockwise)

Rates and accelerations are therefore inches/sec, deg/sec, etc. Inches are used because FIRST field drawings are usually spec'd in inches, so it makes for intuitive autonomous mode scripting. We use degrees for angles due to intuition. 0 degrees is north because usually if we care about degrees we are talking about autonomous mode, so the robot's starting orientation defines the coordinate system.

I've played with libraries like Boost Units and javax.units, but always found their syntax clunky.