Ground-penetrating radar (GPR) is a non-destructive geophysical method that uses radio waves to create a subsurface image. An antenna transmits electromagnetic pulses into a surface, and a receiver records the reflected signals to detect objects and changes in material properties beneath.

• GPR signals lose energy quickly in electrically conductive materials like wet clay or salt-contaminated soil. This severely restricts penetration depth, sometimes to only a few centimeters.

• The antenna frequency is a compromise between depth and resolution. Higher-frequency antennas provide better resolution for shallow objects, while lower-frequency antennas penetrate deeper but with less detail.

• GPR can indicate the presence of an object but cannot identify its specific material, such as distinguishing a gas line from a water pipe. This often requires supplementing GPR with other locating methods.