Big thx Jon for providing this!
Got an article idea: would love to see something on Slope.
We all know rangefinders “calculate” adjusted or plays-like distances for elevation. How?
Full disclosure, I’m an (ex)engineer and obsessed how golf works. Example: 150y uphill par3, rangefinder says plays-like 160y. Ok, so
how can plays-like not take trajectory into account?
My assumption is trajectory (land angle) determines plays-like more than distance.
Currently, I do what you suggest: use Google Earth (and Inkscape) to make yardage books. I discovered the altitude feature in GE and include elevation change relative to the green, ex: “150-2” meaning 150 yards and 2 yards downhill.
Ok, now the hard part, how to implement this info. Based on empirical observation (I always notice where my pitchmark is relative to ball) and Trackman website, I determined that most short irons/wedges come down pretty steep, say 60*. Mids probably 45*. So, maybe longs/hybrids/fw woods 30*?
From trig, the distance is function of angle and height. 45* would obviously be 1:1 ratio; 60* is 1: 0.5 and 30* is 1:1.7 roughly. I made a chart (fits in yardage book holder):
Uphill HiTraj MidTraj LoTraj
5 3 5 9 (One line excerpt)
To use, I read elevation from my yardage book, determine straight-line distance to my target and estimate trajectory. I then look up on my chart to find the distance to add/subtract to straight-line distance. Example:
Take our uphill par3 above. From my yb, I read +5 yards (relative to green) for my tee box. I’ll probably be playing 7ish iron, meaning mid traj. From chart I read 5 yards plus 150 to my target (center of green!) = 155 yards total. Perfect 7 for me.
Any ideas on an improved formula and/or method, or any insights would be greatly appreciated! Again, thx for this!