To the untrained eye, that gadget on the 17th green this morning at Merion Golf Club's East Course must certainly have looked like a bicycle tire pump.
It was, in fact, a device called TruFirm, designed by the USGA's Matt Pringle, Ph.D., and launched eight years ago at the U.S. Open. The purpose of TruFirm? It measures the firmness in different spots of the greens, which aren't so firm right now at soaked Merion, where 5.85 inches of rain has fallen since Friday as they prepare for the first round of the 113th U.S. Open that starts in about 48 hours.
TruFirm, sometimes referred to as The Thumper, works like this, according to the USGA: You pull up a piston, drop it, and a plunger the exact diameter and circumference of a golf ball thumps onto the green while a handheld computer reader attached to it measures the force of the impact.
"It allows us to adjust the firmness by watering them if we need to," says USGA Green Section Director Darin Brevard, in charge of the Mid-Atlantic region, which includes Merion Golf Club. "Before we had this, firmness was determined just by feel. We didn't have concrete measurements you could go on."
TruFirm is deployed mornings and in the evening after play is concluded.