Basal Area - Worked Example

Worked Example

If you carried out a survey using Angle Count Sampling (wedge prism) and you selected a Basal Area Factor (BAF) of 4. And you measured your first tree and its Diameter Brest Height (DBH) was 14cm. Then the standard way of calculating how much of 1ha was covered by tree area (scaling up from that tree to the hectare) would be:

4/((DBH+0.5)² X π/4))

• So this would be 4 - this is the BAF selected for that sampling technique.
• DBH would be 14 - this uses an assumed diameter, when actually used is the radius perpendicular to the tangent line.
• The + 0.5 allows under and over measurement to be accounted for.
• The π/4 converts the rest to the area.

Lastly to see the figure in m² it needs to be multiplied by 10 000. IN this case this means in every Ha there is 242m² of tree area according to this sampled tree being taken as representative of all the unmeasured trees.