Comparison of relative accuracy and time requirement between the caliper, the diameter tape and an electronic tree measuring fork

This study compares the relative accuracy of diameters measured with the caliper, the diameter tape, and the electronic tree measuring fork (ETMF) Tally Boy MC with and without reflector. The time required for the measure and the data entry of diameters to computer for each instrument was also evaluated. Significant differences in mean DBH (diameter outside bark at breast height — 1.3 m above ground) generally occurred among instruments. Nevertheless, even if these differences were significant, they were less than 1 cm for five of the six species tested. For white pine (Pinus strobus L.), however, the use of the ETMF without reflector led to an important overestimation of the DBH in comparison to the caliper, the diameter tape and the ETMF with reflector. The typical fissured bark observed on white pines could probably explain that overestimation. For all species, the addition of the reflector to the ETMF decreased the differences among instruments. The measures taken with the diameter tape were slightly larger than those made with the caliper. In comparison to the diameter tape and the caliper, the ETMF reduced the time required for date collection from 35 to 45%. Key words: diameter measurement, timber inventory