Comparison of field methods and models to estimate mean crown diameter

The direct measurement of crown diameters with logger's tapes adds significantly to the cost of extensive forest inventories. We undertook a study of 100 trees to compare this measurement method to four alternatives-two-field instruments, ocular estimates, and regression models. Using the taping method as the standard of comparison, accuracy of the tested alternatives was adequate for softwood species, but short of the specified measurement quality objective for estimating the mean crown diameter of hardwoods. Due to savings infield costs, ocular estimation and regression models were the best alternatives to direct measurement with logger's tapes.