driveshaft angles

**** if I know. I haven't measured it yet. The 9" swap has yet to be done. Setting the pinion at 5 degrees is how I've done it for forty years and I've always been damn close.......right on the money a few times. Everybody's scared of 5 degrees initial pinion angle, but they fail to realize, that backs off a hair when you install the rear end on the leaf springs.
When you set your pinion at 5 degrees, is that measured relative to the ground? If not what is the 5 degrees relative to?