Test data acquisiton of air-coupled GPR, Can road sub-grade information be effectively recorded in 3D with georadar at traffic speed? Part of R&D project “Infrastructure in 3D” in cooperation between Innovation Norway, Trafikverket and TerraTec Författare: TerraTec, Report 4C Part of the R&D project “Infrastructure in 3D” in cooperation between Innovation Norge, Trafikverket and TerraTec, Report 4C