Ground radar - How does it work?

Ground-penetrating radar

Ground-penetrating radar or ground radar is a method of using radar waves to look down into the ground to identify materials with different properties. The image shows equipment consisting of an antenna that lies against the ground, control electronics and a computer to control the equipment and collect data. The antenna consists of a transmitter antenna and a receiver antenna. The signal is sent out from the transmitter and the equipment measures the time it takes for the signal to return to the receiver. The received signal then contains reflections from objects in the ground which can then be interpreted and provide an image of what the ground looks like.

What can be identified are differences between different materials and material properties in the soil, in other words, it is not possible to directly see What it is what is in the ground, it is just that there is something that deviates from the ground in general. What you can see is, for example, differences in density, such as a grave where the surrounding soil is tightly packed while the grave fill material is looser. You can also see objects with different electromagnetic properties, such as metals. The method is therefore sometimes used to map buried cables and pipes. Since the method is based on radar waves, the frequency you examine means that you can see at different depths in the ground and that the size of the objects you can identify needs to be of a certain size to be visible.

Magnetometry or gradiometer measurement

A magnetometer or gradiometer is a very sensitive device that measures small changes in the natural magnetic field. This means that anything in the ground that can disrupt the magnetic field will be identified as a deviation from the normal field. Obvious objects that distort the magnetic field are metal objects, which means that the measurements must be made without metal objects such as trouser buttons, zippers or cars being nearby, a car can interfere at a distance of up to 15 m. Metal objects in the ground will of course be identified, but also fire sources as high temperature can change the magnetic properties of the soil material so that it distorts the field.

The data collected needs to be interpreted by an expert who can also read out much more depending on the relationships between the deviations that are seen.