The following report demonstrates the accuracy of using Ground Penetrating Radar (GPR) to determine both the surface layer thickness for asphalt, and concrete pavements. In addition tests were conducted to identify GPR’s repeatability on dry pavements, GPR’s ability to determine pavement layer thicknesses in wet conditions, and an attempt was made to determine the number of actual field cores necessary to accurately post-process radar data into thickness values. The equipment used to perform these evaluations was Geophysical Survey Systems Inc.’s model SIR 10B with the model 4108 (1 GHz.) air-launched horn antenna. Preliminary results indicate that when ground truth cores were used, GPR calculated thicknesses varied from actual core thicknesses by: Asphalt less than two inches: o +/-10.32% to +/-0.40% o +/-0.20 to +/-0.01 inches Asphalt bases of eight to nine inches: o +/-2.73% to +/-1.34% o +/-0.24 to +/-0.12 inches Concrete nine to twelve inches: o +/-14.24 to +/-0.05% o +/-1.66 to +/-0.01 inches The results from the additional test mentioned above may be found inside this report.