Innovation and Reliability Since 1980

Ground Solutions

Our Technologies

Potassium Magnetometers

Highest Precision and Absolute Accuracy
For the Advanced User

Overhauser Magnetometers

High Quality and Sensitivity
Cost Effective

Proton Precession Magnetometers

Affordable and Robust
Good Quality and Repeatability

VLF Electromagnetics

Up to 3 Frequencies at a time
Now Providing Shallow Resistivity Sections

Ground Magnetometer and Gradiometer Solutions

Ground geophysics continues to play a key role in subsurface explorations in a variety of fields. It is an essential tool for verifying airborne anomalies which cannot resolve the complex features that magnetometers/gradiometers can achieve on the ground. Ground geophysics therefore has an economic role to play–ensuring that follow up drill targets are placed appropriately so that they maximize the opportunity for meaningful results.

In addition, ground geophysics is useful in smaller, more restricted areas that do not call for expensive airborne geophysics. Increasing automation (that allows larger areas to be surveyed by ground using carts and other technologies) is a meaningful approach for surveying cost effectively and with high quality data and results.

While it is anticipated that airborne solutions will continue to evolve, ground solutions are also evolving as is discussed in this short overview of GEM’s ground magnetometers and gradiometers.

GEM’s Approach to Ground Solutions


GEM’s Potassium system features a novel
backpack-mounted solution with sensors,
electronics and cabling all self-contained.
System is designed for “hands-free”
operation to save time and effort.

Although GEM started initially with airborne work, it quickly became a leader in ground magnetometers and gradiometers based on early versions of its Proton and Overhauser systems. Now, GEM is pleased to offer the most comprehensive set of ground magnetometer solutions. This solution set includes advanced Proton, Overhauser, and now, optically pumped Potassium magnetometers and gradiometers.

GEM’s line of advanced Proton, Overhauser and Potassium units is designed to offer our clients exactly the range of functionality that they require. For example, GEM’s one-of-a-kind Proton system is accepted as an entry-level system for many organizations – allowing them to perform basic functions with good sensitivity (i.e. a versatile tool for many investigations).

On the other hand, Overhauser offers extremely low energy consumption and excellent sensitivity–making it a robust, mid-range tool. And Potassium, with its fast sampling, and ultra-high sensitivity and gradient tolerance making this an ideal instrument for more demanding applications.

When choosing a solution, whether it be a Proton, Overhauser or Potassium configuration, you can be assured that your solution will be tailor-made to the challenges you face–giving you a reliable alternative in the face of competing options which do not allow as much flexibility.

GEM makes every attempt to advise our clients and potential clients on the value of the solution being selected. For example, Overhauser and Potassium systems offer fast sampling which can be used for automation as opposed to Proton systems which do not offer this capability. This shows some of the value of higher order systems as opposed to Proton–the entry-level system.

Innovation in Ground Magnetometers


GEM Overhauser magnetometer in the field
with sensor shown and GPS receiver at top.
System is mounted in a backpack for
easy hands-free operation.

From its early days, as you review our corporate history, GEM has always been a leader in the World of Magnetics. One of GEM’s “firsts” include the development of the first “Walking Mag”. A walking mag is one where the operator is equipped with a GEM unit that automatically samples during the walking process. This gives a nearly continuous record of the ground over which the survey is being conducted.

The main advantages are continuous coverage as well as speed and efficiency–a walking survey basically doubles the daily production over a “walk, stop, read, and walk” system. GEM’s Walking functionality has been duplicated with varying degrees of success by several competitors but there is still nothing better than a GEM original version based on the R&D work that is ongoing.

GEM has also led with its Overhauser technology – an innovative technology developed from first-principles by GEM’s founder and owner. Overhauser has been responsible for many economic discoveries in mineral exploration as well as archeological treasures located or rediscovered through magnetic surveys with GEM instruments.

Overhauser offers a unique blend of features and benefits as it is low power, not subject to orientation errors, is rugged and more. For additional information, please see the Overhauser write-up included in the Products section of this web site.

The company was a leader in adopting “hands-free” backpack devices that enable users to carry a magnetometer or gradiometer throughout the day in a portable, easy-to-use fashion. It enables hands-free operation which promotes safety and efficiency. In general, these specialized backpack systems offer a wide range of value and ease in surveying. Traditional poles are also available.

A further GEM development was the advent of the optically pumped Potassium magnetometer.  Potassium offers a thin spectral line of operation–meaning that Potassium sensors have minimal heading error.

Potassium also offers an order-of-magnitude increase in sensitivity, significantly higher gradient tolerance and more, including fast-sampling up to 20 Hz.

These developments continue as GEM conducts ongoing research into all of its technologies with the objective of advancing the boundaries of magnetic surveying even further on the ground.

Automation as the Key to the Future

Increasingly, companies and individuals are seeking to streamline their surveys and obtain meaningful results faster and with less effort. Standard walking surveys as invented by GEM are an excellent solution where there are 8 to 12 km of surveying to perform daily; however, it is also possible that clients may be seeking higher productivity.

This can be accomplished through automation in a number of ways:

  • Integrate your system with a Bluetooth solution for recording direct to handheld device
  • Use a GEM 4-wheeled cart with sensors mounted on the cart
  • Use an alternate platform for housing the sensors and maneuvering them (ex. ATV).

Several of our users are pursuing Bluetooth-type solutions, particularly in Australia where new technologies are particularly welcomed. In addition, more are turning to special non-magnetic cart technologies to effectively survey larger areas using the fast sampling rates provided in Overhauser and Potassium systems.

Ground VLF

GEM is also pleased to offer a ground VLF system, consisting of three coils mounted on a backpack. This system can monitor up to three transmitting stations and automatically records information. This system can be run on its own, or it can be integrated into any of our ground magnetometer systems. (Proton, Overhauser, or Potassium) for efficient multi-parameter surveying.

The recently upgraded system now features an electronic tilt system rather than previously used fluid-filled sensors that do not respond as quickly nor are they as accurate.

For Your Next Survey

For your next survey, we recommend that you carefully consider the options available from GEM.

Generally, we suggest Overhauser systems for many subsurface investigations as it has an attractive set of features and benefits, including robustness. Overhauser also offers fast-sampling for automation.

Alternately, a Potassium system may be appropriate where ground parameters are subtle, such as subtle structural mapping in gold exploration, or other targets such as archaeological artifacts. Potassium also offers very-fast sampling.

And GEM’s Proton systems offer a reasonable, entry-level approach to surveying with this versatile magnetometer/gradiometer. It does not offer automation; rather it is carried in a backpack or pole-mounted configuration.

The proof of GEM’s technologies lies in the high quality data produced, the economic gains realized through our products, and our warranty. With a full two-year warranty, we take pride in our systems and quality–dedicated to our clients and their pursuit of subsurface discoveries. At GEM, Our World is Magnetic!

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