Diagram to illustrate points, lines, and triangles needed in measuring tree height

OBSERVATIONS:

1. ENTS method is to measure BG of triangle ABG and DE of ADE.

2. Clinometer only users sometimes try to form ACD and ADE.

a. These users recognize that B is not over the trunk of the tree and consider

the tree's true height to be CE.

3. Other clinometer only users treat B as though it were directly in line with CE

a. These users make large errors when BF is much closer to AH than is CE

4. Crown point cross-triangualtion seeks to locate point F

ASSUMPTIONS:

1. AG and AD are level with point A, so GD is level

2. HF, HE, and FE are gound lines

PROBLEMS:

1. Locate F, measure FE, and compute horizontal component of FE

2. Derive useful results from these relationships

NOTE:

1. My 8.3-foot average error calc was derived from

a. Using angle BAG

b. Distance AD

c. Height = Tan(BAG) x AD

2. Many tangent based calcs do not incorporate this error, but many do

ADDITIONAL NOTES:

1. Laying out line HFK will allow useful computations and comparisons to be made.

2. Line HK can be established with two people and a long tape measure.

a. Person #1 directs person #2 to follow the line from H to beneath the crown point and beyond using a plumb bob.

b. Person #2 carries a tape measure laying it on the ground and creating line HK.

c. Locating point F can be done by computing AG and where possible stretching the tape and hold it level with Person #1's eye until F is reached.

d. If the point B can be seen from a sufficiently separated spot, a second tape can be run beneath B and where the  tapes cross is F

3. If F can be located relative to AH, all kinds of useful calculations can be made and relationships derived.

4. In addition to the dendrometer work and ordinary height measuring, I hope to develop a sample of 100 trees of varying species and shapes

for which heights have been determined and the points F located.

5.John, do you have any time in late Oct and beyond to work on this or a similar experiment?