Height is one of the most important dimensions of trees, but few observers are fully aware of the consequences of the misapplication of conventional height measurement techniques. A new approach, the sine method, can improve height measurement by being less sensitive to the requirements of conventional techniques (similar triangles and the tangent method). We studied the sine method through a couple of comparisons. First, we demonstrated the validity of the sine method under idealized conditions by comparing tangent and sine measurements on a stationary object of a known height. Then, we compared heights collected via climbing and lowering a tape from the highest point of a number of forest-grown trees with heights measured with the sine method. The sine method offers a viable, cost effective alternative to traditional measurement approaches, especially for large or leaning trees, and for trees with broadly spreading crowns.
Bragg, Don C.; Frelich, Lee E.; Leverett, Robert T.; Blozan, Will; Luthringer, Dale J. 2011. The sine method: an alternative height measurement technique. Res. Note SRS-22. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 11 p.