Ground diameter/cm

Number

Percentage

<0.5

41

19.2%

0.5

56

26.3%

1

67

31.5%

2

24

11.3%

3

14

6.6%

4

2

0.9%

5

4

1.9%

6

1

0.5%

7

2

0.9%

9

2

0.9%