Measuring tilt of tree structural root zones under static and wind loading

This paper describes a non-destructive method to measure the tilt angle (Φ) of a treeʹs structural root zone as it tilts under winds or static pulling. This method records both magnitude and direction of the dynamic tilt response of the tree root plate. A tri-axial accelerometer is used as a tilt sensor and is attached to the base of the tree trunk at ground level. Dynamic root plate tilt can be measured using 20 Hz sampling. The tilt sensor was calibrated in a laboratory then used in field tests on trees that were statically loaded, then on trees subject to natural wind conditions. The maximum structural root zone tilt recorded during static pulling tests was 0.60°. Under natural wind conditions the maximum root plate tilt recorded was 0.88°. Some practical limitations of the sensor in the field due to the battery capacity and reliability are discussed.