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