Green firmness and OM4

In July 2023, I spent a week traveling west across Japan, starting near Tokyo and ending near Fukuoka. Along the way, I collected measurements from nineteen greens on seventeen golf courses. The two courses that had multiple measurements use the 2 green system, and I collected from unique greens on those courses, one green from each type of grass.

I used the Clegg golf course firmness tester to measure the surface hardness of the greens. From the product description:

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