Sine method for tree height measurement employs infrared laser rangefinders to shoot Laser beam towards the tree. It relies on estimates of angles as well as distance from the tree. It is very convenient method especially when it is difficult to reach the tree for measuring distance. This method has been reported to be more accurate and efficient in dense and tall canopies such as hardwood canopy.
Reference: Bragg, D. C. The Sine Method as a More Accurate Height Predictor for Hardwoods. in Proceedings of the 15th Central Hardwood Forest Conference 10 (USDA, Forest Service, Southern Research Station, 2007).