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A way of detecting what is below the surface of the earth, ground penetrating radar (GPR) is an incredible tool for many people. While some of us may have never heard of GPR before, others may know it for a specific application, such as detecting where utility pipes run near their home. In fact, the use of GPR is vast and varied, and sometimes weird and wonderful too.

GPR works by emitting radar pulses through the subsurface as a non-destructive way of anticipating what is there. The idea of the radar itself was first patented in 1904, and the idea for the first radar system to search for buried objects was subsequently patented in 1910, when Gotthelf Leimbach and Heinrich Löwy created the so-called borehole radar. These first systems used a continuous radar wave, and over subsequent years, the pulse radar idea superseded this. Pulse radars were found to lead to better depth resolution.

The idea of GPR didn’t properly take off until after the military started funding research into the technology in the 1970s. One of the most famous first uses for GPR was the Apollo 17 mission in 1972. A GPR called the Apollo Lunar Sounder Experiment (ALSE) was carried by the spacecraft during an orbit around the moon. ALSE was able to record information about what lay below the surface of the moon to a depth of 1.3 kilometers. While GPR technology was able to achieve this incredible feat, other technology was a little further behind at the time. In fact, the information obtained by ALSE had to be recorded on film, as there were no better computer storage options available.

Utility Mapping

Nowadays, most average people may have come across the benefits of GPR due to their utilities. If you have ever bought a property and had surveys done of your land, the maps you received marking pipework and utilities were likely done with the help of GPR. Utility mapping is a crucial part of any building or civil engineering work, as it allows pipework and wires to be located without having to break ground. It allows work to be planned with the location of utilities in mind, and prevents extra costs being incurred from striking pipes and wires by mistake. Anyone embarking on a building project big or small is advised to look into the cost of ground penetrating radar.

GPR is often the method of choice for utility mapping, as it tends to be the most effective method. Electromagnetic Induction (EMI) is sometimes used, and this method uses an electrical current to locate utilities by a process of deflection of the magnetic field created. However, this method can be negatively impacted by various factors, such as metal objects that may be laying over utilities.

Archaeology

GPR also allows us to look for clues under the earth’s surface about histories far older than the laying of pipelines. When used in archaeology, the effectiveness of GPR depends on the soil type, with sandy soils especially conducive to good results. In such conditions, GPR can find archaeological artefacts and features of historical interest. GPR is often used to identify sites that would be promising excavation locations.

Some of the archaeological discoveries made due to GPR are quite incredible. This includes the remains of King Henry I, who was the son of William the Conqueror. GPR was being used to scan a car parking facility near a site of historic interest in England when the remains were found. The reputed tomb of Jesus Christ was also located in Jerusalem using GPR. National Geographic reported that vast sections of the tomb were still intact, despite many centuries of damage and destruction to Jerusalem’s Old City.

Law Enforcement

The ability of GPR to scan the surface of the earth to learn about long-gone civilizations also points to the help the technology can be to more recent mysteries. Law enforcement agencies across the world use GPR to find remains of people, although this is often done in conjunction with intelligence and historical mapping. While hidden graves can be discovered using GPR, police also know that criminals tend to bury evidence, weapons, illegal substances, or money. There are many instances where this technology has discovered these sorts of items that are crucial to ongoing investigations.

One case in which law enforcement officials used GPR to achieve justice was the kidnapping of a female realtor in England in 1992. Michael Sams was the kidnapper, after he arranged to meet the victim at a property under false pretenses. Police agreed to meet Sams with a ransom payment of £175,000, with a plan to catch the criminal without handing over the money. However, Sams managed to take the money and escape. Following the release, police were able to recover £150,000 of this money, after finding it buried in a field using GPR.