UBC Theses and Dissertations
Comparison of absolute and relative standard errors and estimates of tree volumes Hejjas, Joseph
A great many kinds and forms of volume equations can be found in any review of the literature on this topic. At least four procedures are available for comparing volume equations to judge which one gives the best estimate of volume. These procedures are evaluated in this thesis for seven volume equation forms: [equation forms omitted] and two new methods are introduced: (l) Taylor's series for estimating errors and (2) sum of absolute deviations. Comparisons of above equations with different procedures were carried out for two species, lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) and white spruce (Picea glauca (Moench) Voss.). Merchantable volumes of both species were described by three subsets of data which were grouped according to the following Girard form quotients for 32 foot logs: 1. 80+ 2. 70-79 3. <69. It was found that none of the presently available procedures, including the two new ones, can by itself indicate the best tree volume equation, which led to the conclusion that whenever more than a quick approximation is required, at least two of the methods should be used simultaneously. Both relative and absolute measures of residual variation must be considered. It is concluded that choice of equation form depends very much on the specific requirements of the research or operational project involved.
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