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Green speed is probably the most frequently measured piece of data related to putting green performance. It is a measure of playing conditions that is easy to understand, inexpensive to collect, and provides information about how maintenance practices and agronomic programs affect the golfer experience. Characteristics like firmness and smoothness are also important factors in putting green quality, but until recently golf courses have had limited options for taking those measurements in a reliable way. For these reasons, green speeds are a consistent point of focus for superintendents, green committees, course owners and the golfing public.

Collecting green speed data can help superintendents achieve consistency across greens, maintain appropriate speeds for the course design and the golfers playing it, and minimize disruptions due to maintenance practices. These are all good things. However, it is important to note that faster does not necessarily mean better, and more than a few courses have created problems for themselves by pushing too hard for speed.

Like any part of your data collection program, green speed measurements are only as good as the method used to obtain them. Increased precision in measurement produces more-accurate results, which can be used to make better decisions about maintenance practices. However, consistency and precision can be hard to obtain in the real world. Staff are often under time pressure while collecting data and many courses have different people collecting green speed data throughout the week. They may use slightly different techniques or different locations to take measurements, which can lead to variation in the data that doesn’t necessarily reflect what is happening with the greens.

"Like any part of your data collection program, green speed measurements are only as good as the method used to obtain them."

We recently experienced a good example of these issues with one of our GS3™/DEACON® customers. They were using the GS3 to take traditional Stimpmeter measurements with a tape measure and comparing those with the GS3’s digital measurements on the same rolls. If you are unfamiliar with the GS3, it is a new “smart golf ball” developed by the USGA that uses internal sensors to measure green speed, firmness, smoothness and trueness. For green speed, the GS3 measures deceleration of the ball and translates that to a physical distance. It does not measure the actual distance the ball traveled. When the superintendent in this case encountered unexpected variation between the physical and digital measurements, we took a closer look at the data. What we found was quite interesting.

On Figure 1 below, you’ll see a horizontal line at 13.7 revolutions per second. This is how fast the GS3 (or a golf ball) should be rolling off the Stimpmeter when the tool is used correctly – i.e., slowly lifting and then stopping and holding still when the ball leaves the notch and rolls down the ramp. The actual exit velocity averages at the course in question measured by the GS3 are highlighted by red marks around this horizontal line, with each shape indicating the operator that performed the data collection that day. The resulting physical roll distance averages for each day are captured in yellow, while the GS3-reported distance averages are in blue.

On days where the actual exit velocity is faster than ideal – meaning the Stimpmeter was raised too quickly or too high – we see larger differences between tape measure distance and the GS3’s calculation of roll distance. This happens because the GS3 is determining roll distance with sensors that assume the correct release technique. Operators A and E (red circles and diamonds on the chart) were generating faster-than-ideal ball speeds with their Stimpmeter techniques, which led to the observed variability.

The discrepancy between tape measure distance and GS3 digital measurements raised a couple of important points. First, it highlights the impact users can have on data collection. Two staff members using improper techniques led to exaggerated green speed measurements with the traditional tape measure reading. This can create various management and communication issues depending on how green speed measurements are used at the course. However, tracking green speed data and noting the users who took the measurements allowed the superintendent to identify the inconsistency and train the staff on proper technique, leading to a better data collection program and staff with improved skills.

"Two staff members using improper techniques led to exaggerated green speed measurements with the traditional tape measure reading."

The second important finding from this data is that improper technique affected the tape measure green speed measurements more than the GS3’s digital readings. While there was initial concern that the discrepancy between tape measurements and digital measurements might indicate a malfunction in the GS3 unit, it may have highlighted a benefit of the tool – greater resistance to user error. We were intrigued by that possibility and decided to test that hypothesis.

To test the GS3’s resilience to operator technique, we conducted an experiment using exaggerated exit velocities. We identified two flat, uniform spots on a putting green and performed five rolls each at slow, normal and fast exit velocities. To achieve each set of launch speeds, we modified the angle between the Stimpmeter and the turf when the ball started rolling. For fast rolls, we continued raising the Stimpmeter after the ball left the notch, and for slow rolls we lowered the Stimpmeter as soon as the ball left the notch. The average tape measure and digital distances from each set of launch conditions are described in Figure 2.

The GS3 green speed measurement (blue line) stayed consistent around 9 feet regardless of whether we lifted, lowered or kept the Stimpmeter properly still at the moment of release. The tape measure speed (orange line) had almost 6 feet of variability depending on the improper technique used. The correct technique intersected almost exactly with the GS3 measurement. This shows that even with intentionally improper technique, the GS3 measurements of green speed remain consistent while tape measure readings do not.

"The second important finding from this data is that improper technique affected the tape measure green speed measurements more than the GS3’s digital readings."

Conclusion

One of the principal advantages of data collection technology is offering more consistency across users. We saw this as maintenance teams moved from using soil probes to portable moisture meters for measuring putting green moisture, and we may now see the same benefit from using a tool like the GS3 instead of traditional tape measurements to collect green speed data. However, it is important for anyone measuring green speed with any tool to understand the influence of consistency in data collection procedures and to strive for using the proper technique. The GS3 is not immune to using improper locations and/or technique, and following the correct Stimpmeter procedure is always recommended.

Data collection is a skill that requires training and experience to develop – the same way that it takes time and practice to learn how to properly mow a green, set up the course, or operate any of the complex pieces of equipment used in course maintenance. Investing time and effort into developing robust data collection practices will give you more accurate information about your facility, which you can use to make better decisions about your operation.