Arboriculture & Urban Forestry 48(6): November 2022 human error can result from deviation from the meth- ods’ best practices or from inaccuracies in determin- ing the highest point on the tree. Spending additional time to walk around the tree and determine the high- est point is integral to measuring a more accurate total tree height. Several conditions exist for the use of the stick method. In using the stick method, the ground between the tree and the observer must be level, and the top of the tree must be close to true vertical above the base of the tree. Any deviation from the 2 prior conditions will result in error in estimated tree height using the stick method. Should the tree’s top not be vertically above the base, the stick method will yield an overestimate when the assumed right angle is actu- ally acute and an underestimate when the angle is obtuse. The amplification of error with leaning trees will be most influential when the tree leans directly towards or away from the position of the observer. Similarly, should the ground between the tree and the observer not be level, the stick and clinometer methods will yield an overestimate, provided that the observer and the base of the tree are at the same level and a depression or ridge exists between the observer and the tree’s base and the measuring tape is laid on the ground. Because both methods are contingent on the abil- ity to measure the horizontal distance accurately using a measuring tape, their application will also be limited by hindrances to measuring a clear path from the observer to the tree trunk. As such, the use of the stick method or clinometer when working in an area with large brush accumulation can be limited. How- ever, when used in a felling scenario, where the mea- surer wants to know where the top of the tree is likely to reach, foot placement where the top of the stick aligns with the top of the tree from the measurer’s perspective will roughly estimate the felling radius of the tree, as is true when the clinometer reads 45°. This same situation with large brush accumulation is also detrimental to the use of the rangefinder, how- ever. The measurer must be able to determine the location of the base and trunk of the tree, and this may not be possible with interference between the base and/or trunk of the tree and the rangefinder. In an urbanized environment, this may be less frequently encountered, although shrubbery surrounding the tree can impede the application of the rangefinder. In such cases, a second person can stand next to the trunk of 329 the tree and provide a reflective point for the range- finder. Alternatively, the stick method or clinometer can be used with the measurer making use of a mea- suring tape to measure from the base of the tree to a position where a clinometer can be used or at the 45° angle with a stick. This introduces another benefit of the clinometer over the stick method: the ability to use the clinome- ter at varying distances. As the clinometer is not con- tingent on maintaining a 45° angle, the clinometer can be used at a closer range than the stick method. Additionally, elevation corrections for the clinometer are more readily determinable, although requiring additional measurements of the distance parallel to the slope and the degrees of slope (Rheinhardt et al. 2013). In much the same manner that statistical tests hold various assumptions and conditions, so too do the measuring instruments in urban forestry. The founda- tional condition which underpins the use of the range- finder is a clear, unhindered ability to see the tree’s trunk, base, and top. Any hindrance to viewing the trunk can cause the laser pulse to misread, resulting in inaccurate measurements by distorting the true hori- zontal distance, thus detrimentally impacting the tan- gent functions which yield tree height. The clinometer and the stick method share the condition that the mea- surer must be able to measure using a tape measure along a horizontal gradient, although the stick method has the further condition that the measurer must main- tain an isosceles right triangle. The overarching bene- fit of the stick method is that it comes at no cost and a stick can be sourced by an arborist at most every job site, while the rangefinder is more accurate and faster to use, yet more expensive, although the cost may be offset by the swiftness of the tool. Meanwhile, the cli- nometer finds itself as an intermediary between the 2 others. CONCLUSION This study demonstrates the accuracy and precision of the rangefinder above the clinometer and stick method. While the rangefinder was determined to be the most accurate, the clinometer was close in accu- racy. The 2 methods were closer in precision to each other than to the stick method. Using the stick method, reasonable accuracy and precision within the 95% confidence interval was achieved, particularly in mea- suring conifers; however, deviation from the absolute ©2022 International Society of Arboriculture
November 2022
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