TABLE OF CONTENTS Models of the GPR situation range from a simple single frequency evaluation of path losses to complete 3D time domain descriptions of the GPR and its environment. This Chapter introduces some of the approaches and provides a starting point for further exploration of the literature.
Modelling techniques include single frequency models, time domain models, ray tracing, integral techniques (MOM - method of moments) and discrete element methods. The finite-difference time-domain (FDTD) technique has become one of the popular techniques and can be developed to run on most desktop computers with relative efficiency.
The most basic model uses the radar range equation and enables an estimate of received signal level, dynamic range and probability of detection to be assessed. It has significant weaknesses in that most close range GPR systems are operating in the near field or even the reactive field of the antenna (which is also in a bistatic mode), whereas the model assumes a far field model. It is probably more relevant to the longer-range geophysical applications where the target is many tens of metres from the radar. This is described in Section 3.2. A transmission line model, which enables an A-scan representation to be generated, is described in Section 3.3 and is followed by a simulation using a finite-difference time domain (FDTD) method to model the field propagation of a typical GPR system. Sections 3.4 and 3.5 provide further and more detailed examples of modelling methods as applied to particular situations.
Other models are available from...
