"if you learn one thing in college learn a2 + b2 = c2" (AKA the Pythagoras Theorem) So said my college prof. Now all these years later it comes back to haunt me with in of all places hunting...

I use a piece of rope marked at 10,20,30, and 40. I set that from the base of tree and use range markers. Stakes painted to match my sight pins. Radiat out 3 directions and you can pretty much cover everything.