2015 Volume 24 Issue 2 Pages 29-33
Two methods are commonly used to measure the diameter of a tree’s crown or to make tree crown projection figures. One is to measure between points transcribed by eye from the ends of the tree’s branches to the ground below the tree; the other is based on aerial photographs. However, the accuracy and precision of these methods can vary by tens to hundreds of centimeters, as it is difficult to determine the precise locations of these points by eye or from photographs. To address this issue, we developed a new tree crown measurement tool, the Ten-bou-kyou, roughly translated as vertical mirror-eye to the sky. To assess the tool’s accuracy and precision, we used it to measure branch like marks beyond our reach 100 times and compared the results with known reference data. The results using our device differed from the reference data by -1 to 4 cm, with an average of 1.8 ± 1.0 cm. Therefore, we conclude that, despite its slight positive bias, the Ten-bou-kyou may be a promising method for determining the location of points directly below tree branches to within approximately ± 1.0 cm.
