By Geoff Mangum
Generally, the “rule of thumb” math that Break (“) = Distance (‘) * Slope% / 2 (“/%-‘) can be used ONLY when the green surface is only one slope from ball to hole, not several — so the slope is FLAT (although slanted or tilted in gravity out of level) and not concave or convex. But pros use caddie books to try to “figure” break over multiple slopes. How does that work, done correctly?
Caddie books have fall line direction and slope percent in grids over the greens (often in 5’x5’ grids), so a 10-foot putt (120”) might pass over two or three different slope “numbers” (the actual surface changes shape and slope smoothly). So, if the “numbers” are 3% for first third of putt, 2% for second third, and 1% for final third into cup, what is the “effective slope” to use to estimate break and start line?
Crossing two slopes of equal length, weight the first…
Read the rest of what Geoff has to say about Math For Reading Putts Over Multiple Slopes in the September 2018 Monthly Handicap Improver here: