## Abstract / Description of output

Absiruci-In processing GPR data from road surveys the

amplitudes of reflection data have often been used in obtaining

an estimate of the dielectric properties of pavement layers and

consequently an estimate of the layers' thicknesses. The values of

the dielectric constants of the layers are estimated using a

recursive procedure based on assumptions of plane wave

propagation, one dimensional target geometry and that all media

probed by the GPR are low-loss. In practice, this kind of data

processing requires the use of a calibration procedure in the field

which entails the use of a metal sheet placed on the surface of the

ground. This is used in order to provide a reference reflected

GPIl amplitude by assuming that the reflection coefficient of the

metal sheet is known. This reference information is then used in

the recursive determination of reflection coefficients of the layer

interfaces which are then used to obtain values for the dielectric

constants of the layers. Although, the assumption of one

dimlensional geometry (layered earth) appears to be a good

approximation for at least short sections of GPR road data the

other assumptions involved in establishing the processing

procedure may not be as valid and therefore they may have an

effect on the accuracy of the final layer thickness calculations.

This paper presents the results of a numerical investigation into

the accuracy of such processing procedure. Both, a two

dimensional and a three dimensional numerical simulators for

GPIt have been employed to investigate the accuracy with which

valuies of dielectric constants of layered models can be estimated

fronn simulated reflection amplitude GPR data. This relates to

the accuracy of the calculation of the layers' thicknesses which it

shoiild be noted that is the important engineering parameter that

needs to be determined by the GPR survey. Although, )he two

dimensional models employ a theoretical line source as a model

for the GPR's transducers the three dimensional ones employ a

complete model of a GPR antenna. The GPR simulators are

based on the finite-difference time-domain method.

amplitudes of reflection data have often been used in obtaining

an estimate of the dielectric properties of pavement layers and

consequently an estimate of the layers' thicknesses. The values of

the dielectric constants of the layers are estimated using a

recursive procedure based on assumptions of plane wave

propagation, one dimensional target geometry and that all media

probed by the GPR are low-loss. In practice, this kind of data

processing requires the use of a calibration procedure in the field

which entails the use of a metal sheet placed on the surface of the

ground. This is used in order to provide a reference reflected

GPIl amplitude by assuming that the reflection coefficient of the

metal sheet is known. This reference information is then used in

the recursive determination of reflection coefficients of the layer

interfaces which are then used to obtain values for the dielectric

constants of the layers. Although, the assumption of one

dimlensional geometry (layered earth) appears to be a good

approximation for at least short sections of GPR road data the

other assumptions involved in establishing the processing

procedure may not be as valid and therefore they may have an

effect on the accuracy of the final layer thickness calculations.

This paper presents the results of a numerical investigation into

the accuracy of such processing procedure. Both, a two

dimensional and a three dimensional numerical simulators for

GPIt have been employed to investigate the accuracy with which

valuies of dielectric constants of layered models can be estimated

fronn simulated reflection amplitude GPR data. This relates to

the accuracy of the calculation of the layers' thicknesses which it

shoiild be noted that is the important engineering parameter that

needs to be determined by the GPR survey. Although, )he two

dimensional models employ a theoretical line source as a model

for the GPR's transducers the three dimensional ones employ a

complete model of a GPR antenna. The GPR simulators are

based on the finite-difference time-domain method.

Original language | English |
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Title of host publication | GPR 2004, Proceedings of the 10th International Conference on Ground Penetrating Radar |

Pages | 655-658 |

Number of pages | 4 |

DOIs | |

Publication status | Published - Jun 2004 |

Event | Proceedings of the Tenth International Conference on Ground Penetrating Radar - Delft, The Netherlands, United Kingdom Duration: 21 Jun 2004 → 24 Jun 2004 |

### Conference

Conference | Proceedings of the Tenth International Conference on Ground Penetrating Radar |
---|---|

Country/Territory | United Kingdom |

City | Delft, The Netherlands |

Period | 21/06/04 → 24/06/04 |

## Keywords / Materials (for Non-textual outputs)

- Amplitude estimation
- Concrete
- Data processing
- Dielectric constant
- Geometry
- Ground penetrating radar
- Recursive estimation
- Reflection
- Roads
- Slabs