Ground-penetrating radar (or GPR) has a typical maximum depth below ground level (bgl) of 10 m, depending upon the antennae frequencies used, typically 50 MHz to 1.2 Gz. The higher the frequency the smaller the object that can be resolved but also penetration depths decrease, so operators need to think carefully when choosing antennae frequencies and, ideally, undertake trial surveys using different antennae over a target at a known depth onsite. GPR is the most popularly used technique in forensic search, but is not suitable in certain soil types and environments, e.g. coastal (i.e. salt-rich) and clay-rich soils (lack of penetration). 2D profiles can be relatively quickly collected and, if time permits, successive profiles can be used to generate 3D datasets which may resolve more subtle targets (see ). Recent studies have used GPR to locate mass graves from the Spanish Civil War in mountainous and urban environments.
