Innovation and Reliability Since 1980

GEM GSM-19 Cost Effective and High Precision Overhauser Magnetometer



GEM’s Overhauser Magnetometer system is a revolutionary geophysical instrument developed by GEM to offer a rugged, low power, and sensitive alternative to Proton Precession and some other alkali vapour magnetometers.

GEM’s GSM-19 (Overhauser) magnetometer is a primary standard in mineral exploration and magnetic observatories. As a standard for magnetic observatories, this system has proven itself – for its high sensitivity, absolute accuracy and long life. Overhauser magnetometers are also used in archaeology, pipeline mapping, UXO detection, and other engineering and environmental applications.


Overhauser Benefits

The GSM-19 is our mid-range instrument with excellent benefits for subsurface exploration. The Overhauser system offers an order-of-magnitude increase in sensitivity over GEM’s Proton system and matching sensitivities of some alkali devices. With data quality exceeding the standard proton precession, and comparable to the costlier optically pumped cesium magnetometer systems, the GSM-19 is a standard for many applications.

Overhauser magnetometers also provide high absolute accuracy, ruggedness, and reliability – as numerous systems are in operation around the world with an excellent performance record so that the GSM-19 can be counted on in any situation. Early versions of the Overhauser, developed in 1983, are still running on a continuous basis at an observatory in Japan.

GEM Overhauser Magnetometer
GEM’s Overhauser Magnetometer with GPS sensor (top),
console, and backpack. The system is extremely light
and robust – making it an ideal choice for many
subsurface investigations.

Overhauser offers the option of pulsed versus continuous operation. With pulsed operation, the system provides an energizing pulse to initiate the reading. With continuous operation, the system is always active – so that data can be recorded conveniently anywhere, at any time.

GEM’s Overhauser magnetometer/gradiometer also offers much less power consumption than Proton or alkali vapour systems so you can perform a whole day’s work on a single charge. Optional benefits include an omni-directional sensor (i.e. no dead zones) and fast sampling. Fast sampling of up to 5 Hz is available – an important capability for many larger surveys.  This fast sampling gives the option to automate readings on a vehicle such as an all-terrain-vehicle (ATV), snowmobile sled, etc.

The Overhauser Magnetometer does not require maintenance – it is as robust and effective an instrument as ever made for the field. It also has superior environmental specifications, which include an operating temperature of -40°C to +50°C; giving unparalleled performance throughout all survey conditions.

The cables and connectors have been carefully selected for maximum durability and performance. The light weight backpack gives hands-free operation while ensuring a stable, comfortable, and lightweight platform for making measurements.

Integrated GPS

Not only do our GPS technologies tell you where you have been, but they tell you where you need to go. This allows for highly accurate readings via ‘Waypoint Programming’ as well as accurate time synchronization for base station corrections.

With Waypoints, you design your survey on your personal computer and import the stations with ease into the magnetometer console. Then, the system will guide you to each Waypoint where a reading is to be made. With ‘Walking’ mode, you have a nearly continuous record of GPS-referenced data points – a major advantage in surveying because you save time in the field and it eliminates the possibility of positioning mistakes.



Sensitivity: 0.022 nT @ 1 Hz, (0.015 nT option)
Resolution: 0.01 nT
Absolute Accuracy: +/- 0.1 nT
Dynamic Range: 20,000 to 120,000 nT
Gradient Tolerance: Over 10,000 nT/m
Sampling Intervals: 60+, 5, 3, 2, 1, 0.5, 0.2 sec
Operating Temperature: -40°C to +50°C


Add VLF-EM for a complete cost effective multi-parameter survey solution to provide resistivity sections. Please see the VLF brochure

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