Measuring How Much the Tree Leans

Some Basic Measurements

September   1, 2003 -   6.7 degrees
September 22, 2003 - 10.8 degrees
November   30, 2003 - 11.6 degrees
December  30, 2003 - 11.7 degrees
January      31, 2004 - 11.7 degrees
February    31, 2004 - 11.8 degrees
March        31, 2004 - 11.8 degrees
April          31, 2004 - 12.1 degrees
May           31, 2004 - 12.1 degrees

I have tried several ideas to get a good measurement of how much the tree is leaning. The goal has been to develop some measures of how much the lean is changing over time. Upstream View of the Tree The first attempt was putting two small nails into the side of the tree on the side of the tree where the lean would be apparent. There is a string running between these two nails. A second string is hanging with a fishing weight on the end. As the tree increases it's lean it will move the weight to the side. The distance from the second nail will become of measure of the increased lean.

The second measurement involves placing a stake in the ground at the base of the tree. A fishing weight hung from the first nail now is directly over top of the stake as seen in the photo on the left. As the tree increased its lean the weight will shift to the right.

Upstream View of the TreeBoth of these methods have a problem. As the tree falls it will take a chunk of the ground around the base of the tree with it. This will be the soil bound to the roots of the tree. So the second nail in the tree will move with the tree. The stake in the ground will also move with the tree.

To correct these problems I place a nail on second tree several feet back from my target tree. I don't expect that tree to move when the first one falls. By measuring the distance between the two trees I will be able to measure how far the tree has shifted.

Upstream View of the Tree The next step was to obtain a measure of how much the tree is currently leaning. For that I brought out my t-square. I hung it on the top nail in the tree and then held it so it ran parallel with the lines on the bark of the tree. The 30" down the t-square I measured how far it was from the string that is hung vertically. A little bit of trigonometry showed a lean of about six degrees. This in only approximate, but it is close enough.

With the measurement of how much the tree leans I can use changes in the positions of the fishing weight and changes in the distance between the two trees to measure the change in the angle of the lean of the tree.

Upstream View of the Tree The final solution was a bit more complex. I placed two nails in the Tulip Popular and another two nails in a second Tulip Popular back about 17 feet from the first. The two nails in the first tree were placed to be parallel the truck. This would give me the lean angle. The two nails on the second tree were placed so they were vertical from one another. By measuring the distance between each pair of nails, that is six measurements, and using the law of cosines and a bit of trig I can place the second tree and monitor the change in how much it leans very precisely. The accuracy of the initial measurement of how much the tree is leaning is a fucation of how accurately I placed the nails on the first tree. The initial measurements with this method gave me a lean of 6.7 degrees - a bit more than the lean of 6 degrees I got with the other methods. I will use the new measurement as the base as I can monitor it's change more precisely.

Finally the photo on the right give a good idea of how much there roots of the tree were exposed to the stream and how much it was leaning on August 16, 2003.

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