I was intending on using the scaffolding angle as a vertical reference for the drain line angle determination. Turns out, the scaffolding is a few degrees off. So I resorted to using two references of workers’ balance in the tilt. They turned out to be more accurate. IN the image you can see a white painted bar line on the wall. That white painted bar line is accurate to vertical. From that, you can see how the scaffolding is tilted slightly to the right in comparison.
I got your intentions and understood them. I just had to chuckle at the scaffold tilt, camera angle and the body positioning of the various humans. It has to be very taxing to work at that inclination for hours.