Trivial point ... however, if anyone is concerned ... the previous ROT calcs mentioned in earlier posts (115 and 120 ft/deg) are both "correct" ... the equation is not linear and it depends on where you look at the tangent ... just to complicate the consideration, I prefer 118 ft/deg ... for rough back of a fag packet mental calcs, 100 ft/deg gives a close enough answer to check if it is worth digging out the takeoff charts from whichever authoritative document takes your fancy ...