TITLE:
Diameter Measurements of the Upper Parts of Trees Using an Ultra-Telephoto Digital Photography System
AUTHORS:
Akira Shimizu, Shigeki Yamada, Yuichiro Arita
KEYWORDS:
Digital Camera, Image Editing Software, Magnifications, Spotting Scope, Taper Curve, Upper Diameter
JOURNAL NAME:
Open Journal of Forestry,
Vol.4 No.4,
July
11,
2014
ABSTRACT: We develop a new
technique to measure the exact upper diameters of trees that is comparatively
simple and inexpensive. We can measure the diameters of entire tree trunks
efficiently and with high precision. The system uses a digital camera with a
~15 - 30× telephoto lens to take a photograph that can be used for measuring the
diameter of the upper part of a comparatively slender tree trunk. Since this
method requires a measuring distance and the height of the target point in the
image, a range finder capable of measuring angles was combined with the main
digiscoping system. A range finder sensor uses a laser and makes a 360 degree
angle of observation possible. The diameter of a target position of the
objective tree can be obtained by measuring the digital image using image
editing software and calculations from spreadsheet software. We focus on the
Japanese cedar species in the southwestern part of Japan. Photographic
measurements were obtained prior to thinning. The estimates that we obtained
largely agree with the true measurements of all trees. With regard to the
estimated accuracy of all measured trees, the maximum error ratio was 7.0%
(1.45 cm), with a ~2% - 4% error for most of the estimated results. Although
the absolute value of the estimation error was 1.87 cm (5.3%) at the maximum
(9.87 m in height and 35.5 cm in diameter), an estimation accuracy of