The most typical data collection is when the Tx-Rx pair (Transmitter and Receiver of the GPR antenna) moves in parallel with the line that you are...

The most typical data collection is when the Tx-Rx pair (Transmitter and Receiver of the GPR antenna) moves in parallel with the line that you are collecting data. When the antenna is in its standard position, metallic targets will appear brighter than non-metallic ones. That leads to radargrams with very bright metallic targets and very weak non-metallic targets. Sometimes, the reflection from the metallic targets can disguise completely any reflection from nonmetallic ones or can hide the bottom of the concrete slab. This way of data collection is often called in-line data collection.

In order to see non-metallic targets clearer, an antenna can be reversed by 90 degrees to the line (make diagram). Now, the scan is more sensitive to the non-metallic targets. Metallic targets will appear less bright than during the in-line data collection. Concrete slab bottom will also become clearly visible. This way of data collection is called cross-polarized data collection or cross-polarization.