# Introduction

Green speed is defined as

ball roll distance: the distance a ball moves (i) after striking the ground upon termination of its air flight, (ii) as a result of a putting stroke, or (iii) as a result of hand-imparted motion, as in lawn bowling; it can be quantitatively assessed, as by the use of a Stimpmeter on golf greens

This is from Beard, J. B and Harriet J. Beard. 2005. Ball roll distance. p. 40. In Beard’s Encyclopedia for Golf Courses, Grounds, Lawns, Sports Fields. East Lansing, MI: Michigan State University Press.

# Ball roll distance

What we commonly refer to as green speed is measured by ball roll distance from a standard device called the stimpmeter. When the ball rolls a longer distance, the green is said to be faster.

# This project

Of course the ball roll distance cannot be the same at every location on a green, or at every location on a set of greens. The ball roll distance—the green speed—varies. But how much variation in green speed is too much? What about variation in speed through the day? The speed at 11 a.m. is unlikely to be the same as it was at 7 a.m.

I’ve been interested in the variation in green speed that can be detected by golf players. A better understanding of what players perceive when green speeds vary by a small amount, or by a large amount, is the primary goal of this project.

The best article I’ve read on this subject is from 2001 by Karcher et al.: Golfer’s perceptions of green speeds vary.

That experiment was conducted with “turfgrass industry professionals attending research field days … [who] volunteered to participate in the green speed perception study.” They concluded that “the average golfer seems unable to detect a 6-inch (15 cm) variation in green speed, regardless of the original speed. Therefore, a 6-inch variation amoing greens is probably a fair definition of consistency on a golf course.”

In this project, we are attempting to measure this difference on golf courses with golf players rather than with golf industry professionals, and are checking this across a wide range of grass types and putting green speeds.