From the source for slip_skid_ball.cxx, the number returned is (-z_accel/y_accel)*10.
For small theta, theta~=tan(theta) when theta is in radians. So the angle of a "ball"
undergoing z_accel and y_accel hung on the end of a string makes with the verticle
will be approximately -z_accel/y_accel radians. Converting to degrees, multiply by
180/pi=57.29, or 5.729 times the returned value. Edited by Dave Perry, 2/26/06.
Edit by Daniel Dubreuil june 2014: I'd rather say
Angle with the verticle (radians) -y_accel/z_accel
FG indicated-slip-skid = -(y_accel/z_accel)*10
-->
<min-deg>-9.3</min-deg>
<max-deg>9.3</max-deg>
<center>
<x-m>0</x-m>
<y-m>0</y-m>
<z-m>0.10</z-m><!-- 0.10 is fitted to the drawing. Initial 0.25 makes the radius of curvature for the glass tube ~10 inches and the angle +-4 deg (more sensitive) -->