The GPR method is based on the use of a measuring device called RADAR, whose name derives from the English words "RAdio Detection And Ranging". Radar devices can detect objects using electro-magnetic waves. The principle of the radar is based on the emission of waves by the transmitting antenna, which after reflection from the boundaries of objects or media comprising the environment return to the receiving antenna and are recorded by the device.

The GPR method allows testing of any medium in which electromagnetic wave propagation is possible, including soil, rocks, ice, building materials such as brick, concrete, asphalt mixtures and wood. Currently, it is widely used in civil engineering and its most important applications include damage detection, correctness of execution assessment and determination of technical condition of building objects and structural elements such as:

• bridges, viaducts, tunnels, culverts and other engineering objects,
• roads, motorways, airfields ,
• railway embankments and ballasts
• masonry and concrete buildings, precast elements,  timber structures ,
• hydrotechnical structures; causeways, dams, levees ,
• industrial infrastructure and plants,
• underground infrastructure (utilities).

The GPR method also finds a number of applications apart from civil engineering. It is successfully used in:

• geology and geodesy,
• mining,
• archaeological research,
• studies of historical buildings,
• hydrology, research on bottom of water reservoirs, glaciers,
• military,
• cryminology,
• detection of soil contamination.

Due to the large number of applications, measurements performed with GPR method differ from each other in the methodology and results interpretation.The differences result from the specifics of the tested objects, the amount of wave attenuation in various media and the nature of the recorded signal interference. The advantages of the GPR method include, first of all, its non-destructive character, possibility of initial assessment of object during the test and measurement speed. Another important matter is ability to obtain high image resolution with limited penetration depth or significant depth of measurement at the expense of limited resolution. These parameters can be improved by using dual or triple frequency antennas.

The GPR method also has its limitations which are, first of all, difficulties in interpretation of the results obtained. This technique requires the operator to have extensive knowledge about the propagation of electromagnetic waves, signal processing, as well as principles of the device operation and construction of the tested structures.

Principle of GPR device operation.