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UBC Theses and Dissertations

Derivation and analysis of compatible tree taper and volume estimating systems Demaerschalk, Julien Pierre


Compatible taper and volume equations give identical estimates of total volume of trees. Two basically opposite techniques for the construction of compatible systems of estimating tree taper (decrease in diameter with increase in height) and volume were derived and examined statistically. In the first method compatible taper equations are derived from volume equations fitted on tree volume data. In the second method compatible volume equations are derived from taper equations fitted on tree taper data. Both systems have been tested for bias in the estimation of diameter inside bark at any height, height for any diameter, section volume and total tree volume. In addition to conventional estimates for all trees, classes representing each fifth of the D²H range were used. No method gave completely satisfactory results for the equations tested. However, a few equations in both systems appear to be sufficiently unbiased to be useful for many purposes. All tests were repeated on data where butt flare measurements were eliminated. Taper equations on these adjusted data showed much less bias over most of the length of the tree bole. Weighting techniques did not produce any significant improvement. Use of non-linear techniques made a small difference in some cases. Meyer's correction factor of the logarithmic volume equation was tested and found to be unnecessary. A good relationship which existed between coefficients from taper and volume equations and form is thought to be useful in certain applications.

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