The amount and angle of roll can be calculated from the ball's velocity, the angle of slope, and the
friction of the putting surface. The force the angle of the plane will exert on the ball varies greatly.
It turns out that the correct angle of offset or "aim" remains the same regardless of distance from the hole.
For example, if the resulting angle of offset is 10 degrees at a distance of 5 ft, it will also be 10 degrees
at a distance of 50ft.
In a controlled environment, we carefully observed the roll of the ball on
greens of different speeds. Specifically, data was recorded on greens with a
stimpmeter rating between 7.5 and 11.5. From the data, we observed a
relationship for ball trajectory and reversed engineered a formula which
accounts for the forces on the ball resulting from friction and the
angle of slope of the green. From this data, we are able to predict the roll
of the ball for a putt with "perfect distance." Perfect distance is assumed
to be the velocity that results in the ball coming to rest 2 ft past the hole.
The application will draw two arcs, one showing the roll of the ball if it were
hit directly at the hole and another arc displaying the angle of offset to aim.
The application correctly accounts for differences in ball trajectory resulting from
the speed of the green, break near the hole, and uphill and downhill slopes.
How does it work?
- Estimate the speed of the green (very slow, slow, normal, fast, very fast)
- Place the device on the ground in front of the ball and tap the screen.
This will record specific data on the slope of the green
(angle of slope left, right, up, down)
Repeat this process at the hole and a few spots in between.
- Move behind your putt and get both the ball and hole in view.
- Press the "analyze" button and the app will compute the path of the ball
and the correct angle of offset to aim.