Comparing Vertical and Horizontal Modes of Importance and Control-Variate Sampling for Bole Volume

Author： Valentine Harry T. Bealle Catherine Gregoire Timothy G.

Publisher： Society of American Foresters

ISSN： 0015-749X

Source： Forest Science, Vol.38, Iss.1, 1992-02, pp. : 160-172

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Abstract

Vertical and horizontal modes of both importance and control-variate sampling for estimating merchantable and total volumes of boles are described and compared. In the horizontal mode, heights are selected at random, and cross-sectional areas are measured. In the vertical mode, cross-sectional areas are selected at random and heights are measured. Estimates obtained by horizontal and vertical control-variate sampling (also known as the critical height method) were equally precise in tests using a proxy taper equation that was linear in cross-sectional area versus height. Both methods gave more precise estimates than did horizontal importance sampling, though the advantage was small for merchantable volume. The performance of vertical importance sampling varied with bole shape. It was the most precise method for some shapes, the least for others. For Sci. 38(1):160-172.