Measuring Tree Sway Frequency with Videos for Ecohydrologic Applications: Assessing the Efficacy of Eulerian Processing Algorithms | CU Experts

Measurements of biophysical tree properties and hydrologic fluxes are; necessary for improving models and monitoring the impact of; disturbances. Prior research has demonstrated that measurements of tree; sway frequency can be used to quantify important ecohydrologic; processes, such as drought stress and snow interception, that otherwise; require expensive measurement techniques. However, existing instruments; used to measure tree sway lack spatial scalability. We investigate; whether the virtual vision sensor and multilevel binary thresholding; video processing algorithms can be used to accurately extract tree sway; frequency at multiple points in a video camera field of view and enable; scalable measurements of ecohydrologic processes. Comparing sway; frequencies extracted from video and accelerometer data at two sites, we; show that for 30-60 s videos, the video processing algorithms can; reproduce accelerometer sway frequencies with ±0.03 Hz accuracy. The; results suggest that video processing algorithms may be suitable for; applications where changes in sway frequency are on the order of tenths; of hertz or larger, for example the measurement of snow in trees.; Further work is needed to clarify the accuracy of the algorithms when; applied to longer videos, which may be required to monitor processes; with more subtle changes in sway frequency, such as diurnal changes in; tree water content.

Ammatelli JH; Gutmann ED; Bush S; Barnard HR; Ciruzzi DM; II SPL; Raleigh MS; Lundquist JD

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