VTA
Visual Tree Assessment, abbreviated as VTA, is a method developed by German professor Claus Mattheck (1947) to examine trees for possible defects that could lead to breakage. In the Netherlands, it is also referred to as Boom Veiligheids Controle (BVC).
This method is also available online.
In Dipla, you can find this form under questionnaires with the name VTA Tree Safety Assessment (Source: Boom7.nl)
Calculations
For all calculations, the Duvigneaud formula is used.
tonnes of dry matter = log(a+b*log(diameter in cm))*1000, where a=2.85102 and b=2.0666
(ref.: Duvigneaud, P., Kestemont, P., Timperman, J. & Moniquet, J.-c. 1977. la hetraie ardennaise a Festuca Altissima a mirwart biomasse et productivite primaire. In: Duvigneaud, P. & Kestemont, P. (eds.). Productivite biologique en Belgique. Editions Duculot, Paris-Gembloux. p. 107–154.)