Tree height measurement methods

Definition : Tree height and related terms
Methods of measuring Tree height
Tree height Measuring Methods

1. Tree height and methods of measurement Submitted to :- Dr. D R Bhardwaj Submitted By :- Bandana Dhiman F-14-20-D FOR- 615 Advances in Forest Biometry Presented By : Dr. Bandana Dhiman Ph.D. wood Sc. & Tech. Dr. Y S Parmar UHF Nauni Solan (H.P.)

2. Tree height It is the vertical distance between the base of the tree and the tip of the highest branch on the tree. It is not the same as the length of the trunk. If a tree is leaning, the trunk length may be greater than the height of the tree. Tree height can be measured in a number of ways with varying degrees of accuracy.

3. Bole height :- is the distance between ground level and crown point. Crown point :- is the position of the first crown forming living or dead branch. Commercial bole height :- is the height of bole that is usually fit for utilization as timber.

4. MEASUREMENT OF HEIGHT Total height of a standing tree is the straight line distance from the tip of the leading shoot to the ground level, usually measured on slopes from the uphill side of the tree. Objectives Height of the standing tree is measured to find out its volume because height is one of the important components of tree volume.

5. METHODS OF MEASUREMENT OF HEIGHT Ocular estimate method Non-instrumental method Shadow method Single pole method Instrumental method

6. Shadow Method

7. Christen’s hypsometer Smythie’s hypsometer Brandis hypsometer Abney’s level Topographical Abney’s level Haga altimeter Ravi multimeter Relaskop Instruments used in measurement of height

8. Instrument based on properties of similar triangle Christen Hypsometer Smythies Hypsometer Instrument based on trignometrical principle Relaskope Abneys level Brandis hypsometer Ravi multimeter INSTRUMENTAL METHOD

9. Hypsometer is an instrument used for determining the height of standing tree from observations taken at some distance from the tree. Altimeters are generally altitude measuring instruments, instrument has been devised to determine heights of trees. Clinometers are instruments which measure angle of slope.

10. Height measuring instruments based on properties of similar triangles are used in India. It consist of a strip of metal, thin wood or even card board about 2.5 cm wide. It has two flanges or protruding edges one at the top and other at the bottom. Each flange has a hole in it, the upper one to suspend the instrument by some thread passing through it and the lower one to suspend a weight from it to prevent it from swinging. It is used with and graduated for a staff of known length. The distance between the inner edges of the flanges varies with instruments used in different countries. The one generally used in India has this distance as 33 cm and is graduated to read yards when used with a staff of 3.6 m(12 ft) . CHRISTEN’ HYPSOMETER

11. CHRISTEN’ HYPSOMETER

12. In order to use the instrument, the observer stands at a suitable place from where both the base and the top of the tree can be seen between the flanges after placing a staff vertically against the tree. He holds the instrument vertically suspended from a thread and moves the hand backward or forward till the top and base of the tree seem to fit exactly within inner edges of the upper and lower flanges respectively. In this position he sees the mark on the instrument where the line of sight to the top of the staff intersects the instrument. the mark reads the height of tree in yards if a 4 yards staff is used or in meters if a 4 m staff is used. When the tree is more than 30 m in ht, the divisions are rather close and mark where the line of the sight from the eye to the top of the staff intersects the instrument is difficult to read. this difficulty can be overcome either by increasing the length of the staff or the instrument, though this will make them unwieldy. METHOD OF USE

13. It is made of flat card boards or thin sheet of wood rectangular or square in shape and provided with a handle. On one side of the board is pasted a squared paper normally of equal length and breadth with the squares parallel to the edge of the board and of size large enough to give at least 3 large square in each direction so that each of its 10 divisions may represent 1m either way and the instrument may read heights up to 30 meters . SMYTHIES HYPSOMETER SMYTHIES HYPSOMETER

14. The vertical scale is called the base or distance scale and is graduated from top to bottom. The horizontal scale is called the height scale and is graduated from the side of the handle to the outside . A plumb bob hangs from the top corner towards the handle side of the squared paper. A part of the protractor is marked on the squared paper showing angles from 0 to 90 °. This helps reading of angles made by the plum bob with the vertical , which is the same thing as the angle at which the board is held to the horizontal while sighting the tip or the base of the tree . On the other side of the board is pasted a table giving percentage deduction corresponding to different angles of depression or elevation to be applied to sloping distance for finding out the horizontal distance .

15. In order to use the instrument in the case where the top of the tree above and the base below the eye level, the observer should stand at a convenient place from where the tip and base of the tree can be sighted. The distance of this point should be measured along ground. The instrument use then pointed to the base of the tree with the handle towards the observer and the angle of depression is read on the protractor. For this angle of depression, percentage deduction is found out from the table given on the back side of the instrument and applied to the measured sloping distance to find out the horizontal distance. now, in order to get the height of the tree below the eye level , the plumb bob should be held on the angle of depression. then the ordinate for the calculated horizontal should be traced till it touches the plumb bob. from this point abscissa should be traced down till the height scale is reached . The reading on the height scale will be the height of the tree below the eye level. then in order to get the height above the eye level , the top of the tree should be sighted with the handle away from the observer. METHOD OF USE

16. The plumb bob should be held at that angle and the ordinate for the calculated horizontal distance traced to the plumb bob and from there traced along abscissa to height scale. The reading on the height scale will be height of the tree above the eye level should be added to get the height of the tree. In case when the base of the tree is above the eye level , both angles will be angles of elevation and so the instrument will be held with the handle away from the observer in both cases . The rest of the procedure will be the same except that towards the end , the height obtained by sighting the base will have to be deducted from the height obtained by sighting to the top . In case when the whole tree is below the eye level , both angles will be angles of depression and therefore the instrument will have to be held with the handles towards the observer in both the cases .the rest of the procedure will be the same except that in the end , the height obtained by sighting to the top will have to be deducted from the height obtained by sighting the base .

17. In India, Brandis hypsometer and Abney’s level, Haga Altimeter and topographical Abney’s level have come in use. More recently, Relaskop, Tele Relaskop, Barr and Stroud dendrometer and Blume-Leiss hypsometer are also being used. INSTRUMENT BASED ON TRIGONOMETRICAL PRINCIPLES

18. The instrument consist of a hollow metal tube about 14cm long and of rectangular cross section. A wheel enclosed in a circular metal case is attatched to it on one side. The object to be sighted is seen through the hollow tube from the end marked a, which is closed except for a horizontal slit through which the observer looks. The other end of the tube marked b is open with a horizontal wire fixed there. The pivoted wheel attached to the tube is heavily weighted on one side W so that when the instrument is horizontal the wheel is in zero position. The outer rim of the wheel is graduated to show degrees which can be read through an opening in the metal case by a magnifying glass in eye piece. The instrument reads angles up to 60 ° above and below the horizontal. To prevent wear and tear as a result of continous swinging of the weighted wheel, the instrument is provided with a retaining spring which presses on the wheel. Only when the spring is depressed, the weighted wheel swings freely. BRANDIS HYPSOMETER

19. In order to use the instrument as a simple clinometers, the observer should stand at a convenient place from where the top and base of the tree can be sighted. He should hold the instrument in left hand and press the spring with forefinger. the top and base should then be sighted successively. in each case, when the wheel becomes steady, the spring should be released to look the wheel. The readings on the scale will give angles to the top and base of the tree. The sloping distance from the observer’s position to the base of the tree should then be measured and height of the tree calculated by any of the formula of the tangent method applicable in the case. METHOD OF USE

20. The instrument is also provided with a table called brandis table which gives the heights of trees directly. This table has been compiled for a specific case where the top of the tree is above and base below the eye level. The table gives the angles of elevation to the top of the tree with an interval of 2°. For each of these angles, a set of angles of depression to the base are given with interval of 5°. Brandis table

21. In order to use the table, it is necessary that the observer should stand at a place from where the angles to the top of the trees is one of the angles given in he table. this can be achieved by moving backward or forward steadily so that the wheel does not swing very fast. when the top has been sighted for any of the angles of elevation given in the table, the instrument should be directed towards the base, having adjusted it to one of the angles of depression given in the table. But care should be taken to see that the position of the observer is not changed. With a fixed position and a fixed angle of depression, the exact base of the tree may not be sighted and therefore the point where the line of sight intersects the tree should be got marked by another man. The height of the mark should be measured and noted down. Then sloping distance should be measures along the ground. The height of the tree from the top to the mark near the base is obtained from the table for the corresponding distance and angles of depression and elevation. the height of the mark is added to get the total height of the tree. METHOD OF USE

22. This is an invaluable instrument for forest officers and is therefore most commonly used by them not only for measurement of heights of tree but also for contour survey in forest surveys and alignment of roads. it consists of a hallow tube with an eye piece fitted at one end and a short sighting tube fitted at the other. The eye piece consists of two or three telescopic hollow tubes with a pin hole at the extreme end. The sighting tube is small detachable tube fitted with a horizontal wire across the centre at the inner end, and a mirror behind the horizontal wire, but covering only half of the tubes, so fitted that it makes an angle of 45°to longitudinal axis of the main tube. The spirit level is fitted to the main tube in such a way that it can be rotated by one screw or a wheel and a screw. when a wheel and a screw are fitted, wheel is for quicker movement and the screw is meant for final adjustments. An index arm is also attached to the spirit level and the spirit level is rotated, the index arm moves on a graduated semicircular arc. the arc is graduated to read whole degrees. Each division of the vernier scale represents 10°(minutes). The number of divisions coinciding with any division on the main scale on semicircular arc, gives the reading in units of 10 minutes. ABNEY’S LEVEL

23. In order to use the instrument, the observer stands away from the tree at the place from where top of the tree the base are visible. then the top of the tree is sighted through the pin hole of the eyepiece after pulling it out. This make the instruments inclined and the bubble is not seen in the mirror. therefore while sighting the top, the screw is rotated to bring the spirit level in the horizontal position, the bubble appear on the edge of the mirror the spirit level is continued to be move slowly to the position when the bubbles image is bisected by the line of horizontal wire on the mirror and in the other half, the tree top is seen touching the horizontal wire. At this position ,the index arms reads the angles of elevation to the top of the tree on the circular arc. METHOD OF USE

24. This instrument is similar to Abney’s level except for minor differences. the protector of this instrument is graduated both sides. one side gives the rise and fall per chain horizontal distance and the other side gives the percentage rise and fall. the instrument is used in combination a trailor tape. Trailer tape is an ordinary tape 1 to 2 chains long on one side it is graduated to read distance while on the other side it gives trailors addition corresponding to various slopes recorded by topo Abney’ level. these trailore addition s represent the distance which must be added to the sloping chain length to make it equivalent to horizontal distance for a particular slope read by topo Abney’s level. TOPOGRAPHICAL ABNEY’S LEVEL

25. While using the instrument on sloping ground the first thing to be done is to stand at one chain horizontal distance from the tree. In order to find out this point, the observer stands at little more than one chain sloping distance and sights the top of staff equal in length to his eye height. for this reading, the trailor addition has to be found from the trailor tape .then one chain sloping distance + tailor addition read, gives the point which is at a horizontal distance of one chain one tree. The top of the staff may be sighted once again from new position to se that there is no change in the reading of the topo Abneys level. if there is any change, the position is readjusted with the new trailor addition. from this new position, the line of sight to the top will give height of the base from eye level. The height of the tree is then found out adding to the two readings in cases where the top of the tree is above and base below the eye level or subtracting the latter from the former reading in cases where the top and the base are above eye level or subtracting the former the latter in cases where the top and the base of the tree are below eye level. METHOD OF USE

26. It is a portable instrument for measuring heights of trees or other vertical objects without the trigonometric tables and formulae as required for determination of heights by Abneys level. It consists of a gravity controlled, damped, pivoted pointer and a series of rotatable scales on a hexagonal bar in a metal, pistol shaped case. the top of the case is slightly rounded at the rear end of which eye piece s with a pinhole and towards the font end a sight vane, consisting of a hollow metal tube 1.5 cm long and 2m in diameter and having two prongs R protruding from the opposite sides inside the tube. the pronges are in a horizontal line with a slight gap between the two. A little below the rounded top, the instrument has inside it a hexagonal bar which can be rotated by a turning knob on the front face of the instrument in line with the bar inside. HAGA ALTIMETER

27. Relaskop is used for measurement of basal area of crops. the instrument can also be used for measuring diameters over bark at any height and heights of tree. the instrument has a rotating drum for slope correction. This drum is used for height measurements. four scales for measuring heights are incorporated in the instrument having five measuring bases. One scale gives percentage inclination while the other three scales used in collaboration of measuring bases 03,04 and 05. It gives directly height of the tree when a horizontal stick of fixed length kept at the base of the tree is exactly covered with the selected measuring base. RELASKOP

28. LiDAR LiDAR, an acronym for Light Detection and Ranging, is an optical remote sensing technology that can measure distance to objects. LiDAR data is publicly available for many areas and these data sets can be used to display tree heights present on any of these locations. Heights are determined by measuring the distance to the ground from the air, the distance to the tops of the trees, and displaying the difference between the two values.

29. In addition to using LiDAR to locate tall trees, there is great promise for using LiDAR to locate old-growth forests. When comparing known old-growth sites to second-growth in LiDAR, old-growth has a much more textured canopy because of the frequent and often remarkably evenly spaced tree fall gaps. Finding equations that can predict old-growth forests of various types using LiDAR and other data sources is an important area of scientific inquiry that could further conservation of old-growth forest."

30. SOURCES OF ERROR IN HEIGHT MEASUREMENT Instrumental errors. Personal errors. Errors due to measurement. Errors due to observation. Errors due to lean of trees.

31. References Forest Mensuration And Biometry A.N. Chaturvedi & L.S. Khanna Principles and practices of silviculture- L.S.Khanna Indian Forester : Manikanandan and Prabhu www.google.com