A New Method for Forest Volume Measurement with an Electronic Angle Gauge

To realise precise, real-time measurement of forest volume, this study discusses the principles and method of forest volume measurement when utilizing an electronic gauge. Use of the electronic gauge, to count trees within five concentric circles, resulted in a decrease in the variation of estimated forest volume, as the number of circles increased. This estimate became reliable upon reaching the fourth concentric circle. In contrast, the use of a conventional angle gauge revealed no obvious regularity and no significant trend using multiple observation points. As well, for forest inventory plots with uneven spatial distribution, there was relatively low precision when using multiple observation points with a conventional angle gauge: the relative errors of forest volume measurement reached almost 40% in the first plot using multiple observation points. The electronic angle gauge is comprised of a telescope and Charge Coupled Device (CCD) system, which reduced the probability of a misreading and achieved accurate real-time measurement of forest volume. Observers can choose an arbitrary location to position the electronic angle gauge. The survey time with the new method was half that of using a conventional angle gauge at five different observation locations. The forest volume measurement was automated using a Personal Digital Assistant (PDA) with newly-designed software capable of identifying, registering and then counting the trees in a plot. This method improves accuracy of forest volume measurement and reduces the time and effort required previously.