For those tracking your own scopes note the following
Leica DISTO D2 laser accurate to 1/64 of an inch at 100 yards. Being off by 1 yard is one percent error out of the gates and COMPLETELY unacceptable so you have to be accurate down to at least 1 foot if not 1 inch in your distance to the tall ruler. Dont use your standard rangefinder. Get a Leica or run a 100 yard tape straight and taught. My Vectronix PLEF15 measures this distance (84 yards) with an error of 1-2 yards!
Make sure the tall ruler is perfectly level
Test the scope over 30 MRAD or 96 inches if possible. You’re trying to magnify minuscule errors in each click and 10 MRAD is barely enough clicks.
Make sure the apparatus you rest in is completely immobile. The one pictured weighs 25# and has a 26# lead brick atop it and sits atop a 300# concrete block. Overkill, but you get the point
OTOH if you’re not shooting ELR none of this matters. If you want to know whether or not such precise measurements of tracking error are worth it, figure out the farthest you’re going to shoot and how many MRAD elevation are needed for that shot and then see how many clicks a one percent error will throw you off in either direction. if it is too little to matter, don’t bother measuring unless it is purely mental masturbation, or to feel confident in your scope, or to have bragging rights of how well it tracks
Perhaps the worst thing you could do is half ass this procedure in 30 minutes, get a result that has a one or 2% error built into it from sloppy inputs, adjust your clicks for that, and make your system less accurate than it was to start out; you want this procedure to increase click accuracy, not decrease it.