brickpi.py question

[burf2000]

Could I just ask what unit of measure the model dependences where

#Model dependend settings
PI=3.141
ROBOT_WIDTH=0.16
WHEEL_DIAMETER=0.055
WHEEL_RADIUS=WHEEL_DIAMETER/2
WHEEL_PERIMETER=2PIWHEEL_RADIUS

mm, cm, meters, inches

Also why is this times 1000
PWRDIV=1000*RPS