Measuring Green Speed with iOS Devices

 Marcus Jones, PhD, Iowa State University and 

 Quincy Law, Graduate Student, Purdue University 

The iStimp App
By now, you have probably heard of the iStimp, an app developed by iGolfApps.com, to measure green speed. The iStimp is available to anyone who has an iOS device such as an iPod Touch, iPhone, or iPad for a nominal fee of $0.99. A stimpmeter reading is obtained by rolling a golf ball off the iOS device and measuring the distance the ball travels with a built in ruler. The iStimp application then uses algorithms to generate a stimpmeter value.

With over 250 million iOS devices sold to the public, the iStimp may have already appeared at your facility. If not, chances are you will at some point in the future. The question is, does the iStimp produce stimpmeter readings equivalent to what you generate with the USGA stimpmeter? A study conducted at Iowa State University set out to answer that question.

How we did it
Our study was conducted on a practice putting green at a local area golf course. The turf was a mixture of creeping bentgrass and annual bluegrass mowed at 0.125 inches.  Wind speed was negligible during the test.

Stimpmeter readings were obtained using the iStimp app with an iPad 2, iPhone 4, and iPod touch 4th generation. The USGA stimpmeter was included as a control along with a research stimpmeter which is known to produce equivalent stimpmeter readings.

Three people, each with varying experience using stimpmeters, operated each device. All accessories (cases, ect.) were removed from each iOS device with the exception of screen protectors.

A level area of the green was selected and a tee was inserted at the end of the measurement device. Three golf balls were released, one at a time, from each device according to the guidelines suggested by the manufacturer. Titleist Pro VI golf balls, each weighing within one gram of the others, were used in this study.

The distance each golf ball traveled was measured from the end of each device to the front of the golf ball. The built in ruler function was used with the iOS devices and a measuring tape was used to record ball roll for the USGA and research stimpmeters. This length was recorded for each golf ball and the average obtained. The same three golf balls were rolled in the opposite direction along a similar line and the same measurements and calculations performed.

Accuracy of the iStimp
The green speed of the putting surface was 12 feet according to the USGA stimpmeter (Figure 1). This device is the only tool accepted by the USGA to measure green speed. The research stimpmeter produced a statistically similar reading of 11.8 feet. Research stimpmeters have proven to yield green speed values similar to the USGA device. The fact that the USGA and research stimpmeters produced statistically similar values in our experiment verifies our technique.

The three iOS devices equipped with the iStimp app failed to produce stimpmeter values similar to the USGA device (Figure 1). The iStimp application when utilized on the iPad 2 underestimated stimpmeter readings by 9%. In contrast, the iStimp application overestimated stimpmeter readings on the iPhone 4, and iPod touch 4th Gen. by 21 and 16%, respectively.

Figure 1. Stimpmeter readings for five devices used to measure putting green speed.  Columns with different letter are statistically different.  Note: Stimpmeter readings are listed in feet: 14.5 = 14’6”.

If golfers approach you and want to discuss stimpmeter readings obtained from the iStimp, take the time to find out which device they used. While the iPad 2 generated readings most similar to the USGA stimpmeter, this seems the least convenient device to obtain stimpmeter readings with due to its size and expense. There are probably far more iPod’s and iPhone’s that find their way onto golf courses and each of these devices will overestimate stimpmeter readings.

Regardless of the iOS device used, stimpmeter readings obtained with the iStimp app on the iPad 2, iPod touch 4th Gen. and iPhone 4 are different compared to the USGA stimpmeter and comparisons are not valid.

KIRKWOOD SPRING TURF WORKSHOP

Nick Christians
Feb. 17, 2012

Here is a post from Troy McQuillen about a workshop that they have planned at Kirkwood on March 8. It looks like a good program. Hopefully some of you will be able to attend.

Winter Weather Update 2-13-12

Some facilities have received snow cover while others remain open to the winter conditions.

Now it’s finally starting to feel like winter. The high temperatures in central Iowa barely crept out of the teens over the weekend. Wind chills brought the temperature down into the single digits and the low temperatures were some of the coldest we have experienced so far.

Records from the National Weather Service indicate that the average temperature in Des Moines from December 1, 2011 through January 31, 2012 was 31.7 degrees. That mark is tied for Des Moines’ third warmest winter and just falls short of the warmest average on record of 32 degrees, set during the winter of 1918-1919. This year ranks eighth in Waterloo, fifth in Mason City and is tied for sixth warmest winter in Ottumwa.

Unusual winter weather conditions have been the norm.  January saw three days in the 60's and nighttime temperatures never fell below zero.

Over the last 100 years the temperature has only reached 65 degrees in January six times. Two of those were this year, and for only the second time since tracking began, temperatures climbed into the 60s on three days in January.

Nighttime low temperatures have also been higher than usual. The lowest temperature recorded in Des Moines so far this winter has been one degree above zero, only the fourth time in 134 years the temperature hasn’t reached zero by the end of January.

Needless to say, this weather has been confusing to plants as many trees have already put out buds. Many of you are wondering how your turf is holding up in these conditions. Some of you received snow cover the weekend of February 4th but others continue to deal with open conditions. Snow cover will help protect the turf from desiccation. Injury from desiccation continues to be the number one cause of concern this winter especially on perennial ryegrass and short cut creeping bentgrass. Desiccation is most common in late winter/early spring when the ground is still frozen and the turf is exposed to drying winds.

One of the best ways to check on the health of your turf during the winter months is to sample turf from high value areas such as putting greens or from areas where the turf has experienced damage in the past. Collecting turf samples when the ground is frozen requires the proper tools. We have a sawzall, and a heavy duty hammer and chisel that we use to remove cores of turf from frozen soil. I collected some turf samples from our research station on the last day of January and brought them into our greenhouses to check the health of the turf.

I collected samples of greens height turf from different rootzones along with creeping bentgrass and perennial ryegrass at fairway height. The plugs collected from the putting greens received a late fall topdressing heading into winter. The fairway height turf did not receive any topdressing. We have had minimal snow cover at our research facility this winter and our turf is exposed to northwest winds.

The good news is that even with very little snow cover this winter, all the plugs greened up after a week in the greenhouse. The greenup came from exiting leaf tissue regaining its color and from new growth from the crown of the plant. Even without a greenhouse you can conduct a similar test at your facility by sampling cores of turf, giving them some water and keeping them in a warm spot with some light. This is a great way to gauge the health of your turf during the winter and can give you an idea what to expect once the snow melts.

These plugs sampled from the field in late January had no trouble greening up after a week in the greenhouse.  Top picture taken January 31, 2012.  Bottom picture taken February 7, 2012.

Marcus Jones
Assistant Scientist
Iowa State University

2011 Awards and Scholarship Recipients

Congratulations to all the 2011 Award and Scholarship Recipients.  If you would like to nominate someone in 2012 visit www.iowaturfgrass.org to find information and nomination forms from the Iowa Golf Course Superintendent, Iowa Sports Turf Managers, and Iowa Professional Lawn Care awards.   

Iowa Golf Course Superintendents Association

Distinguished Service Award - Ken Ellenson, CGCS, Amana Colonies Golf Course

Ken Ellenson, CGCS  (center) with Randy Robinson (left) and Brett Parcher (right).

Superintendent of the Year - Nick Cummins, Westwood Golf Course

Nick Cummins (right) with Randy Robinson (left).

Environmental Stewardship Award - Terry Hannah, Superintendent, Jester Park Golf Course

Terry Hannah (center) with 2010 recipient Rick Tegtmeier, CGCS (left), and Randy Robinson (right).

Charles Calhoun Writing Award - Jon Christenson, Superintendent, Monarch Bay Golf Club (not pictured)


Iowa Sports Turf Managers Association

Iowa Sports Turf Manager of the Year - Tim Van Loo, CSFM, Iowa State Athletics

Tim Van Loo with wife Amber, son Steven, and daughter Sam.

Iowa Baseball Field of the Year - Rick House, Sports Field Manager, Council Bluffs Recreation Complex

Rick House (center) with Tony Senio (left) and Zach Smith (right).

Golden Cleat Award Recipient - Bryan Wood, Owner, Commercial Turf & Tractor

Bryan Wood (right) with Tony Senio (left).

Iowa State University Scholarship Winners

Adam Grimm - A.E. Cott and Charles Hall Scholarships

Adam Grimm (right) with Greg Harkin (left).

Kevin Hansen - Iowa GCSA Legacy Scholarship and ISTMA Scholarship

Kevin Hansen (right) with Tony Senio (left).

Shane Lohman - Bob Clark Scholarship and Iowa GCSA Scholarship

Shane Lohman (right) with Randy Robinson (left).

Joe Parker - Bob Clark Scholarship and Kevin Reiter Memorial Scholarship

Joe Parker (right) with Randy Robinson (left)