Imagine you are grinding this hideous knife
http://imgur.com/a/oTXDN
We start at the green section, connect our jig, set the angle, and proceed.
Next we move onto the blue section. I like to grind with the edge perpendicular to the belt, so now the jig is rotated is 45° from its initial position (along the 'roll' axis).
Next we move onto the red section. Now the jig is rotated 90° from its initial position (along the 'roll' axis).
If the jig measures the angle between level and current position (like the Bubble Jig), then the reading is incorrect - this is NOT equal to the angle between the platen and the steel when we are grinding the blue and red sections.
Does your jig measure the angle between level and current position, or does it take into account rotation of the jig along the 'roll' axis?