Land surveying is a detailed study or inspection of land through observations and measurements using several tools and techniques. Before starting any construction work, it is an important task that needs to be done to know about the characteristic of a land. The planning and design of all civil engineering projects such as highways, bridges, tunnels, dams etc. is based on surveying and measurement. These help understand national and state boundaries, chart coastlines, navigable streams and lakes, establish control points, execute hydrographic and oceanographic charting and mapping, prepare topographic map of land surface of the Earth, collect field data, prepare plan or map of the area surveyed, analyze it and calculate the field parameters for current and future engineering works.
Land survey is done using several tools and techniques, one of which is Ground Penetrating Radar (GPR).
What is Ground Penetrating Radar?
Apart from understanding what is above the ground, it is also important to know what lies beneath it. For this purpose, Ground Penetrating Radar is used as it provides information about the land’s subsurface.
Ground Penetrating Radar is a geophysical method that uses radar pulses to image the subsurface. This nondestructive method uses electromagnetic radiation in the microwave band of the radio spectrum and detects the reflected signals from subsurface structures. GPR can have applications in a variety of media, including rock, soil, ice, fresh water, pavements and structures. In the right conditions, practitioners use GPR to detect subsurface objects, changes in material properties, and voids and cracks.
GPR uses high frequency, usually polarized radio waves in the range 10 MHz to 2.6 GHz. A GPR transmitter and antenna emits electromagnetic energy into the ground. When the energy encounters a buried object or a boundary between materials having different permittivity’s, it is reflected back to the surface. A receiving antenna can then record the variations in the return signal. The principles involved are similar to seismology, except GPR methods implement electromagnetic energy rather than acoustic energy and energy may be reflected at boundaries where subsurface electrical properties change rather than subsurface mechanical properties as is the case with seismic energy.
Uses of Ground Penetrating Radar
It is often very costly and time-consuming to relocate and reroute underground infrastructure. It disturbs the surrounding environment and also causes traffic delays. So it is very important to understand what is buried inside and then plan and design the underground infrastructure. There are several methods for that, for example, electromagnetic locators, excavators, among others, but then again they are not sufficient to give the overall information and are costly too.
In comparison to other survey methods, GPR has emerged as one of the best technologies that provides accurate assessments. It is less intrusive and can locate pipes and serve as a powerful visual aid in underground diagnosis without digging, probing, or drilling of any kind.
GPR is useful in all utility applications, be it clay pipes, plastic or PVC, concrete pipe, metal pipe, missing valves, water boxes, abandoned lines, illegal or unknown connection, conduit, water, wastewater, gas, power, telecommunications wire, fiber optic, septic tanks, voids or manholes.
Ground Penetrating Radar has great importance in the exploration and mining industry, especially with regards to subsurface mapping. In mining, GPR reduces extraction costs. With efficient methods like borehole investigation, the technology can be leveraged to gain information from great depths at an affordable cost. The surveying system helps in identifying rock quality, determining mining safety, establishing bedrock depth, ascertaining rock quality, mineral exploration, groundwater exploration, fractures characterization etc.
GPR also helps to accurately locate underground structures before carrying operations. In deep mine applications, the system is vital for identifying geologic features that may be potential areas for rock bursts, like for example fractures, shear zones and faults.
Before planning any construction work, accurate subsurface information is a must. It is of utmost importance to identify underground utilities to avoid any problem. That is where the GPR technology comes to the rescue. The technology is capable of detecting and identifying non-metallic as well as metallic utilities, helping project managers to understand the subsurface and avoid risk at further stages.
During the construction process, the system is helpful in locating the bars embedded in structural elements, sub-surface voids and delamination. The system is useful not only in assessing structural concrete elements, but also in soils and masonry buildings, ancient monuments as well as locating buried pipes and ducts.