Step 1: Camera setup
Drill a small hole into the spoil board. Then:
Machine->Camera->Set offset->Mark /4801
Now start the camera:
Machine->Camera->Show Camera ... /480
Centre the camera crosshairs over the hole, at lowest possible Z height.
Machine->Camera->Set offset->Read 1 /4802
Increase Z as far as possible while still being able to see the hole, and re-centre the crosshairs.
Machine->Camera->Set offset->Read 2 /4803
This sets up the camera so that you can accurately place your spindle over a job or read off co-ordinates for transformation of tool paths (used later). It uses two points to compensate for possible mis-alignment of the camera, which would shift its apparent position when Z height is altered.