Comparison between predicted volumes estimated by taper equations and true volumes obtained by the water displacement technique (xylometer)

Abstract

The objective of this paper was to compare volumes estimated by taper equations to true volumes obtained by the water displacement technique (xylometer). Four previously published models and a fifth-degree polynomial were analyzed. Three sets of diameters measured on 52 fallen trees from Pinus elliottii Engelm. var. elliottii were used to fit the models. Clark et al.'s (1991; USDA For. Serv. Southeast. For. Exp. Stn. Res. Pap. No. SE-282) model was the best to predict diameters along the stem, merchantable volume, and total volumes. Max and Burkhart's (1976; For. Sci. 22(33): 283-289) model also had an excellent performance. The results still showed that the normal comparison between volumes estimated by integration of taper equations to those estimated by Smalian or Huber's formula (usual procedure) underestimates the true error which is achieved by comparison with true volumes (xylometer).

Comparison of model forms for estimating stem taper and volume in the primary conifer species of the North American Acadian Region

“…Thus, the results of this study further suggest that the Clark et al (1991) equation was significantly superior across multiple species at estimating volume when upper stem diameter measurements are available, which supports the results of several other studies (e.g. Filho and Schaaf 1999;Jiang et al 2005). In this present study, the Clark et al (1991) equation reduced the RMSE by 9.3, and 19.5% when compared to the next best equation for balsam fir and red spruce, respectively.…”

“…A relatively limited number of studies have compared the accuracy of stem taper equations in predicting actual stem volume because of the difficulty in measuring the true stem volume. Filho and Schaaf (1999) indicated that the Clark et al (1991) equation was the best at estimating true stem volume (determined with a xylometer) of the models examined in their study. Most studies must obtain observed stem volume by using either Smalian or Huber's formula, which often leads to an underestimation of a taper equation's true error (e.g.…”

“…Most studies must obtain observed stem volume by using either Smalian or Huber's formula, which often leads to an underestimation of a taper equation's true error (e.g. Filho and Schaaf 1999). Although Smalian's formula can be highly biased, its use in this study was believed justified as the distance between observations was taken along the full length of the stem and generally they were less than 2 m apart.…”

Developed of Taper Equation and Volume for Eucalyptus camaldulensis Dem. in the Nineveh Region

“…di=14.2299×h (-0.1873) V 1 = 0.02542(hi) 0.6254 By using the above equations, table (3) was prepared: The above results in Table (4) proved that the technique of estimating the volume of the log pieces of the overall main stem is effective, and the degree of its accuracy [11], and calculating the volume of the wooden pieces for it along the main stem was of high accuracy using the integration method.…”