Use of three-point taper systems in timber cruising

Abstract

Tree volumes and profiles are often estimated as functions of total height and DBH. Alternative estimators include form-class methods, importance sampling, the centroid method, and multi-point profile (taper) estimation systems; all of these require some measurement or estimate of upper stem diameters. The multi-point profile system discussed here allows for upper stem measurements at any heights and constructs a smooth profile prediction that passes through all measurement points. Results from a cruise sample of trees can be summarized to allow for improved profile predictions for the non-sampled trees, which lack upper stem measurements. Decisions must be made on which measurement heights to use, which trees to sample, and how to make the upper stem measurements. The driving forces in sample efficiency are measurement error, between-tree and between-stand variation in form, and within-tree correlations at differing heights. Results from several sources are brought together to illustrate the magnitude of the variances; the focus here is on how to reduce the between-stand errors associated with taper and bark thickness. Suggestions are offered for efficient use of three-point profile systems, addressing measurement techniques, sampling methods, and summarization procedures.

Parent Publication

• Integrated tools for natural resources inventories in the 21st century

Citation

Flewelling, James W.; Ernst, Richard L.; Raynes, Lawrence M. 2000. Use of three-point taper systems in timber cruising. In: Hansen, Mark; Burk, Tom, eds. Integrated tools for natural resources inventories in the 21st century. Gen. Tech. Rep. NC-212. St. Paul, MN: U.S. Dept. of Agriculture, Forest Service, North Central Forest Experiment Station. 364-371.