Iron Rods as Markers for Soil Horizon Depths and Point Scatterers for Estimating Pulse Velocity in GPR Imagery

This work aimed to assess the feasibility of using iron rods as “point scatterers” to identify soil horizons transitions in ground penetrating radar (GPR) images (radargrams) and estimate the electromagnetic pulse velocity from the iron rods hyperbolas in the radargrams. The area is located in Seropédica municipality, Rio de Janeiro state, southeastern Brazil. Five soil profiles were described and classified as Planosols. Iron rods (80-cm long by 8-mm in diameter) were inserted horizontally in the transitions of the soil horizons. Radargrams from the profiles were obtained using a GPR with a monostatic antenna with frequency of 450 MHz. The pulse velocity was estimated by fitting the hyperbolas from the point scatterers caused by the buried rods in the profile radargrams. Depth models were created to convert the radargrams Y-axes from time to depth units and correctly place the soil horizons transitions vertically across the profiles radargrams. The iron rods hyperbolas were clearer, and the pulse velocity was better estimated, in the sandier horizons. Also, the iron rods were useful to mark the depths of the E horizons in the radargrams. Buried iron rods are recommended for estimating the GPR pulse velocity and properly position the radargram features, that is, the soil horizons, in depth.