Efficiency of ultrasonic Vertex III hypsometer compared to the most commonly used hypsometers in Croatian forestry

The article investigates the efficiency of the ultrasonic Vertex hypsometer in tree height measurements in relation to some of the most commonly used hypsometers in Croatian forestry. The whole measurement process consists of three steps: time needed to reach the measurement zone, time needed to determine the distance to a tree, and time needed to measure and read the height of a tree. Measurements were conducted with four hypsometers: Vertex, Blume-Leiss, Bitterlich's Spiegel Relaskop with a standard scale (RO) and Bitterlich's Spiegel Relaskop with a CP scale (with the horizontally /RCPH/ or vertically /RCPV/ positioned staff). Research results do not show any statistically important differences among the hypsometers in terms of time needed to reach the measurement zone. In measuring tree heights in a stricter sense (without the element of reaching the measurement zone), the least amount of time was required by the Vertex (28.4 cmin) on average. The Vertex is followed by the relaskop with a CP scale, the horizontally (57.4 cmin) or vertically positioned staff (86.1 cmin), then the Blume-Leiss (84.0 cmin) and finally the relaskop with a standard scale (106.8 cmin). The differences between the Vertex and other hypsometers are statistically significant. Despite a slightly higher price of the Vertex, its speed, precision, accuracy and simplicity of use, as well as the possibility of simple circular plot forest inventories rank it above all the other instruments.