JIAN WEN et al: DETECTION AND MEASUREMENT OF INTERNAL DEFECTS FOR TREE TRUNK BY GPR

Application of Ground Penetrating Radar (GPR) in tree trunk internal defects test is technically a Non-destructive Detection (NDT), especially suitable for the measurement of old and rare trees. The living trees complex internal structure makes the wooden medium highly anisotropic and heterogeneous. GPR uses the principle of the scattering of the electromagnetic wave which propagates through the medium and is reflected from object. The velocity of the scatter signal is determined primarily by the permittivity of the material which is influenced by water content and density. For rising the precision of NDT to old willow internal detects, in our investigation, we analyse the model of relationship between the dielectric constant and the moisture content of the ancient willow, the model was used in maintenance experiment of ancient Salix babylonica at the Summer Palace Beijing China. The test results indicate that the precision of internal defects measurement can be improved to 5% by using the relationship model, without which the precision is beyond 10%.