|
Trees have a wide variety of sizes and shapes and growth habits. Specimens may grow as individual trunks, multitrunk masses, coppices, clonal colonies, or even more exotic tree complexes. Most champion tree programs focus finding and measuring the largest single-trunk example of each species. There are three basic parameters commonly measured to characterize the size of a single trunk tree: height, girth, and crown spread. Additional details on the methodology of Tree height measurement, Tree girth measurement, Tree crown measurement, and Tree volume measurement are presented in the links herein. A detailed guideline to these basic measurements is provided in (The Tree Measuring Guidelines of the Eastern Native Tree Society ) by Will Blozan.〔Blozan, Will. 2004, 2008. The Tree Measuring Guidelines of the Eastern Native Tree Society. http://www.nativetreesociety.org/measure/Tree_Measuring_Guidelines-revised1.pdf Accessed March 4, 2013.〕〔Blozan, Will. 2006. Tree Measuring Guidelines of the Eastern Native Tree Society. Bulletin of the Eastern Native Tree Society, Volume 1, Number 1, Summer 2006. pp. 3-10.〕 Summaries of how to measure trees are also presented by various groups involved in documenting big trees around the world. These include among others: a) American Forests Tree Measuring Guidelines;〔American Forests Measuring Guidelines. http://www.americanforests.org/bigtrees/big-tree-measuring-guidelines/ Accessed March 4, 2013.〕 b) National Register of Big Trees - Australia's Champion Trees: Tree Measurement, Champions and Verification;〔National Register of Big Trees, Australia's Champion Trees. http://www.nationalregisterofbigtrees.com.au/tree_measurement.php Accessed March 4, 2013.〕 c)Tree Register: A unique record of Notable and Ancient Trees in Britain and Ireland - How to measure trees for inclusion in the Tree Register;〔Tree Register: A unique record of Notable and Ancient Trees in Britain and Ireland - How to measure trees for inclusion in the Tree Register. http://www.treeregister.org/measuringtrees.shtml Accessed March 4, 2013.〕 and d) NZ Notable Trees Trust.〔NZ Notable Trees Trust, Measuring Trees. http://www.notabletrees.org.nz/pages/14/Measuring-Recording-Trees Accessed March 4, 2013.〕 Other parameters also measured include trunk and branch volume, canopy structure, canopy volume, and overall tree shape. Overviews of some of these more advanced measurements are discussed in Blozan above and in “Tsuga Search Measurement Protocols” by Will Blozan and Jess Riddle, September 2006,〔Blozan, Will and Riddle, Jess. September 2006. Tsuga Search Measurement Protocols. http://www.nativetreesociety.org/tsuga/tsuga_measurement_protocols.htm Accessed March 4, 2013.〕 and tree trunk modeling by Robert Leverett〔Leverett, Robert T. 2007. A new look at tree trunk modeling: old formulae and new. Bulletin of the Eastern Native Tree Society, Volume 2, Issue 4, Summer 2007, pp. 5-11.〕 and Leverett and others.〔Leverett, Robert T.; Blozan, Will; and Beluzo, Gary. 2008. Modeling tree trunks: approaches and Formula. Bulletin of the Eastern Native Tree Society, Volume 3, Issue 2, Spring 2008, pp. 3-13.〕 The appropriate measurement protocols for multitrunk trees and other more exotic forms are less well-defined, but some general guidelines are presented below. ==Height== (詳細はTree height measurement〕 There are direct measurements. Shorter trees can be measured using a long pole extended vertically to the top of the tree. Larger trees can be climbed and a tape measurement made from the highest point of the climb to the base of the tree. The distance to the top of the tree can be measured from that point, if needed, using a pole. Historically the most direct method of finding a tree's height was to cut it down and measure it prostrate on the ground. Tree heights can also be measured remotely from the ground. The most basic remote height methodologies are all variations of the stick measurement.〔Champion Trees of Pennsylvania, Measurement. http://www.pabigtrees.com/Measure.aspx Accessed March 4, 2013.〕〔Champion Trees of Pennsylvania, Measurement Notes. http://www.pabigtrees.com/measure_notes.aspx Accessed March 4, 2013.〕 The height is calculated using the principle of similar triangles. A short stick is held out pointing vertically at arm’s length by its base pointing vertically. The surveyor moves in and out toward a tree until the base of the stick above the lower hand aligns with the base of the tree and the top of the stick aligns with the top of the tree. The distance from the lower hand to the surveyor’s eye is measured, the distance from the lower hand to the top of the stick is measured, and the distance from the eye to the base of the tree is measured with a tape. The ratio of distance from the eye to the hand is to the distance from eye to the base of the tree, as is equal to the ratio of the length of the stick to the height of the tree provided that the top of the tree is positioned vertically over the base. (distance from eye to base of tree/distance from eye to base of stick) x length of stick = tree height A second method uses a clinometer and a tape and is commonly employed in the forestry industry.〔Environmental Education, How to Use a Clinometer. http://elms.smcps.org/student-tutorials/great-trees/using-a-clinometer-to-measure-height Accessed March 4, 2013.〕 This process applies the trigonometric tangent function. In this process the horizontal distance is measured to the trunk of a tree from a sighting position. The angle to the top of the tree is measured with the clinometer. horizontal distance at eye level to the tree trunk x tangent Θ = height above eye level If the tree extends below eye level the same process is used to determine the length below eye level and that is added to height above eye level to determine total tree height. Different clinometers have different reading scales, but all apply the same function. Calculations are as above if it reads in degrees. If it has a percentage scale, then the percentage is multiplied by the distance to the tree to determine a height or extension above and below eye level. Others have a 66’ scale where if used at a distance of 66 feet from the tree the height above or below eye level can be directly read from the scale. Errors frequently accompany this type of measuring. The process assumes that the top of the tree is directly over the base of the tree. The tree top may be offset significantly from a point directly over the base (or level point on the trunk). Typical errors from this effect are often on the order of 10 to 20 feet. A bigger problem is misidentifying a forward leaning branch for the actual top of the tree. Errors associated with this mistake may yield measurements that are off many tens of feet and some errors of over forty feet and more have made it onto various champion tree lists, and in at least two cases, the errors have exceeded 60 feet.〔Rucker, Colby. 2008. Great Eastern Trees, Past and Present. Bulletin of the Eastern Native Tree Society, Volume 3, Issue 4, Fall 2008, pp. 6-40.〕〔Mismeasured Trees. http://www.nativetreesociety.org/measure/notes/mismeasured_trees.htm Accessed March 5, 2013.〕 A third remote method is called the sine-height method or ENTS method.〔〔〔Frank, Edward Forrest. January 12, 2010. The Really, Really Basics of Laser Rangefinder/Clinometer Tree Height Measurements. http://www.nativetreesociety.org/measure/really_basic_3a.pdf Accessed March 4, 2013.〕 It requires the use of a laser rangefinder and clinometer. In this method the distance to the top of a tree is directly measured by the surveyor using the laser rangefinder. The angle to the top is measured with the clinometer. The height of the tree top above eye level: (= sine Θ of angle x distance to the top ) the same process is used to measure the extension of the base of the tree below or even above eye level. Since the measurement is along the hypotenuse of the right triangle and both the top and bottom triangles are independent, it doesn’t matter if the tree top is offset from the base as this does not affect the calculation. In addition the top branches of the tree can be scanned with the laser rangefinder to find which top is actually the tallest and the major error of misidentifying the top can be avoided. If the true top of the tree is misidentified the height measurement for the tree will simply be short by some amount, and will not be exaggerated. The height will be correct for the target being measured. With calibration, multiple shots, and a technique to deal with scales that read only to the nearest yard or meter, tree heights can typically be measured to within one foot using this methodology. Other measurement techniques include surveying with a transit and a total station, extended baseline method, the parallax method, and the three verticals method.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「tree measurement」の詳細全文を読む スポンサード リンク
|