Bob, Bart,

I am just wondering about the interpolation. If the tree were vertical with the upper measured value for the trunk directly over the base, then the height would be sinA x hypotenuse = tanA x horizontal distance to the trunk. If the section from the top to the bottom as shown on the photograph were broken down into equal length segments, each segment would have the the same number of degrees of angle but would be of different lengths. But then you could go back and use the tangent function to determine the height of each of those points, and thus determine the segment length between each of the interpolated lengths. If the tree were slanted from vertical but still straight, then this process would give you the base length of a similar triangle with a length of trunk = hypotenuse = arctan (angle from base to uppermost measurement). So the length of the trunk segments could be calculated if the tree were straight and either the upper and lower measured sections were directly over each other, or if the section was tilted and you were looking in the same plane as the tilt angle. A 10 degree slant in the tree would only affect the calculated length by 1.5% so minor irregularities on the trunk will not make that much difference. So segment length could be calculated if you treat interpolated points as angles and work from there.

Ed