Angle counting sample

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The angle counting is a sampling method of the forest inventory .

The angle counting test is used to determine the number (N) of trees within a virtual test circle whose breast height diameter (BHD) exceeds the counting width (Z from 1,2,4). This virtual test circle thus varies for each tree and its radius can also be determined from the BHD .

The angle count sample is used to determine the base area of ​​the stand by tree species (G = N * Z), which, in connection with the age of the stand, is used to derive the degree of tillering (B °) on the basis of yield tables (ET).

The process was developed in the 1940s by the Austrian forest scientist Walter Bitterlich . Originally, a measuring plate attached to a string was used to target the trees ( thumb bearing ). All trees within a sample circle that appear wider than the measuring plate are counted. The simple dendrometer ("little Kramer") according to Kramer can be used for this purpose, for example. Bitterlich developed the process further using the mirror relay (1948), which also allows the slope to be corrected easily . In practice, wedge or cruising prisms are often used for the angle counting test.

The advantage of the procedure is its efficiency. As thicker trees are more likely to be selected than thinner trees, performing an angle counting test in young stands takes significantly less time than recording fixed sample circles if the stand area is to be determined with sufficient accuracy in old stands at the same time. Angle count samples were used in the German federal forest inventory (1987 and 2002).

In mixed forest stands , species with weaker growth are systematically underrepresented in the angle count sample. The method is therefore less suitable for structures with a lot of structure .

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