For this purpose the diameter of a tree is to be ascertained by measuring it (over its bark) at 1.5m above ground level – in the case of a multi-stemmed tree, it is the diameter of the largest stem.
At y diben hwn, mae diamedr coeden i'w ganfod drwy ei mesur (dros ei rhisgl) 1.5m uwchben lefel y ddaear – yn achos coeden aml-goesyn, dylid mesur y coesyn mwyaf.