Primary Magnetic Field Used to Induce an Electrical Current in the Earth


Electromagnetic Induction uses a primary magnetic field which induces an electrical current in the earth. The current in the earth produces a secondary magnetic field. The characteristics of the secondary magnetic field indicates the conductivity of the earth.

The wide range of frequency selections available with EMI, and its complimentary use with GPR, allow it to be a useful aid in a variety of professionally supported surveys and investigations including:

  • Geological Mapping (Geologic)
  • Groundwater Exploration (Hydrogeology)
  • Contaminant Detection (Environmental)
  • Landfill and Hazardous Waste Site Investigation (Environmental)
  • Metal Detection (UST, Buried man-made objects)
  • Precision Agriculture

The Electromagnetic Induction has an internal GPS unit. Having the internal GPS we are able to compile the data and map out the location of the finding per the latitude longitude given. To the right is an example of what the data will look like. In this map there are several locations of concrete on the site.

Electromagnetic Induction technology is a great additional service that GPRS can offer along with our Ground Penetrating Radar Services. Electromagnetic Induction is best used in open fields or parking lots covered with asphalt.

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EMI Applications:
• Locating buried metal objects (drums, USTs, utilities, etc.)
• Delineating Contamination Plumes
• Investigating landfills
• Identifying backfilled areas and trenches
• Detecting buried building foundations
• Pollution plume mapping

For many of these applications, Electromagnetic Induction can be used hand-in-hand with other GPRS methods such as ground penetrating radar (GPR) to broaden the information gathering and to better the identification of subsurface anomalies or to differentiate structures.

EMI Benefits:
The EMI process is useful for locating buried ferrous and non-ferrous material. The benefits of Electromagnetic methods are:
• Large sites are scanned quick and easy, making EMI cost-effective.
• Non-destructive and non-invasive
• Portable, with little to no effects on the environment
• The onsite real-time data allows for preliminary anomaly identification
• No ground contact required. Eliminates direct electrical coupling problems and allows for more rapid data acquisition.

Electrical Duct Bank Image
Electrical Duct Bank
Unknown Buried Conductive Anomalies Image
Unknown Buried Conductive Anomalies
However, one of the biggest advantages of using EMI are speed and adaptability. Because the EMI instrument is mobile, studies are usually conducted in grids where data are collected by walking a series of parallel lines. This process allows relatively large areas to be thoroughly investigated much more quickly than with other geophysical techniques. One the data is collected and combined, results can be viewed in plan or map view. During the geotechnical phase of a project, this can be very useful in providing optimum well or boring locations. In addition, EMI is a valuable tool to perform cursory or detailed investigations of the upper twenty feet of the subsurface.

UAS Magnetic Imagery:
Now, you can combine both our Electromagnetic Induction service with our new aerial drone services, finding solutions to all your magnetic underground problems!

GPRS’ UAS Magnetic Imagery utilizes magnetometer equipped drones to find abandoned oil well heads to prevent severe fires or damages before breaking ground on your solar farm project. This includes other subsurface hazards including abandoned wells, pipelines, underground tanks, UXO, and more.