reading phsac outputs

can anyone give me more details of the ‘phsac’ module in qnx4 photon ?
y-branch : ok i think this issue is clear
x-branch : what’s the meaning of the numbers
inertia : what does that mean
do not teletype too much. a link with raw information would suffice.
helge … s/sac.html

thanks a lot !
regards helge