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% |