Microwave transmission measurements for estimation of the weight of standing pine trees

An experimental research project was conducted to examine the relationship between microwave attenuation and the weight of standing vegetation. It was found that attenuation measurements using a microwave radio link are highly correlated with the weight of standing Virginia pine trees along the path. A set of control experiments was conducted at 10 GHz. Field measurements were performed in the forest at 12.25 GHz. The equipment used was portable, reliable, and easy to use. By using both vertical and horizontal linear polarizations and retaining only the least depolarized attenuation value, the correlation in the weight-attenuation relationship is improved. The most highly correlated single-weight parameter is oven-dry (or green) weight of leaves and twigs less than 1/2 in in diameter. The method is easily applied to weight estimation. After the weight-attenuation relationship is established by controlled tests, it can be used as an estimator equation together with attenuation measurements to estimate the weight of vegetation in situ.