GSM-19 v6.0 Overhauser Magnetometer / Gradiometer
The GSM-19 v6.0 Overhauser instrument is the total field magnetometer /
gradiometer of choice in today's earth science environment --
representing a unique blend of physics, data quality, operational
efficiency, system design and options that clearly differentiate it from
other quantum magnetometers.
With data quality exceeding standard proton precession and comparable to
costlier optically pumped cesium units, the GSM-19 is a standard (or
emerging standard) in many fields, including:
Taking Advantage of a “Quirk” of Physics
Mineral exploration (ground and airborne base station)
Environmental and engineering
Unexploded Ordnance Detection
Magnetic observatory measurements
Volcanology and earthquake prediction
Overhauser effect magnetometers are essentially proton precession
devices - except that they produce an order-of magnitude greater
sensitivity. These "supercharged" quantum magnetometers also deliver
high absolute accuracy, rapid cycling (up to 5 readings / second), and
exceptionally low power consumption.
The Overhauser effect takes advantage of a "quirk" of physics. This
effect occurs when a special liquid (containing electrons) is combined
with hydrogen atoms and then exposed to secondary polarization from a
radio frequency (RF) magnetic field.
The result is a very strong precession signal that is ideal for very
high-sensitivity total field measurement.
In comparison with proton precession methods, RF signal generation also
keeps power consumption to an absolute minimum and reduces noise (i.e.
generating RF frequencies are well out of the bandwidth of the
In addition, polarization and signal measurement can occur
simultaneously - which enables faster, sequential measurements. This, in
turn, facilitates advanced statistical averaging over the sampling
period and/or increased cycling rates (i.e. sampling speeds).
Other advantages are described later in this page.
The unique Overhauser unit blends physics, data quality,
operational efficiency, system design and options into an
instrumentation package that ... exceeds proton precession and matches
costlier optically pumped cesium capabilities.
And the latest v6.0 technology upgrades provide even more value,
And all of these technologies come complete with the most
attractive prices and warranty in the business!
Integrated GPS option (the only system with fully built-in GPS)
25% increase in sensitivity over GSM-19’s v5.0 system
Enhanced memory (increased by 8 times to 4 Mbytes standard and
expandable to 32 Mbytes)
Programmable base station (for scheduling base stations in one of
Rapid data transfer (using our advanced software)
Internet-based upgrades (from the office or field)
Maximizing Your Data Quality with the GSM-19
Data quality is a function of five key parameters that have been taken
into consideration carefully in the design of the GSM-19. These include
sensitivity, resolution, absolute accuracy, sampling rates and gradient
Data from Kalahari Desert kimberlites. Courtesy of MPH
Consulting (project managers), IGS c. c. (geophysical contractor) and
Aegis Instruments (Pty) Ltd., Botswana.
Sensitivity is a measure of the signal-to noise ratio of the
measuring device and reflects both the underlying physics and
electronic design. The physics of the Overhauser effect improves
sensitivity by an order of magnitude over conventional proton
precession devices. Electronic enhancements, such as high-precision
precession frequency counters (see the v6.0 -- New Milestones
section) enhance sensitivity by 25% over previous versions.
The result is high quality data with sensitivities of 0.015 nT /
√Hz or better. This sensitivity is also the same order-of magnitude
as costlier optically pumped cesium systems.
Resolution is a measure of the smallest number that can be
displayed on the instrument (or transmitted via the download
process). The Overhauser magnetometer displays 7 digits which
includes 5 digits, decimal point and two decimal digits.
This level of resolution translates into well-defined,
characteristic anomalies; improved visual display; and enhanced
numerical data for processing and modeling.
Absolute accuracy reflects the closeness to the "real value"
of the magnetic field -- represented by repeatability of readings
either at stations or between different sensors. With an absolute
accuracy of +/- 0.1 nT, the GSM-19 delivers repeatable
station-to-station results that are reflected in high quality total
Similarly, the system is ideal for gradient installations (readings
between different sensors do not differ by more than +/- 0.1 nT) --
maintaining the same high standard of repeatability. The GSM-19
gradiometer data are consistently low in noise and representative of
the geologic environment under investigation.
Total Field and Stationary Vertical Gradient showing the gradient
largely unaffected by diurnal variation. Absolute accuracy is also
shown to be very high (0.2 nT/meter).
are defined as the fastest speed at which the system can
acquire data. This is a particularly important parameter because high
sampling rates ensure accurate spatial resolution of anomalies and
increase survey efficiency
The GSM-19 Overhauser system is configured for three "measurement modes"
or maximum sampling rates -- "Standard" (3 seconds / reading), "Walking"
(0.5 seconds / reading) and "Fast" (0.2 seconds / reading). These
sampling rates make the GSM-19 a truly versatile system for all ground
applications (including vehicle-borne applications).
represents the ability to obtain reliable measurements
in the presence of extreme magnetic field variations. GSM-19 gradient
tolerance is maintained through internal signal counting algorithms,
sensor design and Overhauser physics. For example, the Overhauser effect
produces high amplitude, long-duration signals that facilitate
measurement in high gradients.
The system's tolerance (10,000 nT / meter) makes it ideal for many
challenging environments -- such as highly magnetic rocks in mineral
exploration applications, or near cultural objects in environmental, UXO
or archeological applications.
Much like an airborne acquisition system, the GSM-19 “Walking”
magnetometer option delivers very highly-sampled, high sensitivity
results that enable very accurate target location and / or earth
Increasing Your Operational Efficiency
Many organizations have standardized their magnetic geophysical
acquisition on the GSM-19 based on high performance and operator
preference. This preference reflects performance enhancements such as
memory capacity; portability characteristics; GPS and navigation; and
dumping and processing.
controls the efficient daily acquisition of data,
acquisition of positioning results from GPS, and the ability to acquire
high resolution results (particularly in GSM-19’s "Walking" mode).
V6.0 upgrades have established the GSM-19 as the commercial standard for
memory with over 262,000 readings (based on a basic configuration of 4
Mbytes of memory and a survey with time, coordinate, and field values).
Optional increments up to 32 Mbytes increase memory to over 2 million
readings -- making the GSM-19 an ideal system for acquisition of data
with integrated GPS readings (when required).
(ruggedness, light weight and power consumption) are
essential for operator productivity in both normal and extreme field
GSM-19 Overhauser magnetometer is established globally as a robust
scientific instrument capable of withstanding temperature, humidity and
terrain extremes. It also has the reputation as the lightest and lowest
power system available -- reflecting Overhauser effect and RF
In comparison with proton precession and optically pumped cesium
systems, the GSM-19 system is the choice of operators as an easy-to-use
and robust system.
GPS and navigation options
are increasingly critical considerations
for earth science professionals. GPS technologies are revolutionizing
data acquisition -- enhancing productivity, increasing spatial
resolution, and providing a new level of data quality for informed
decision-making. The GSM-19 is now available with real-time GPS and DGPS
options in different survey resolutions. For more details, see the GPS
and DGPS section. The GSM-19 can also be used in a GPS Navigation option
with real-time coordinate transformation to UTM, local X-Y coordinate
rotations, automatic end of line flag, guidance to the next line, and
survey "lane" guidance with cross-track display and audio indicator.
Other enhancements include way point pre-programming of up to 1000
points. Professionals can now define a complete survey before leaving
for the field on their PC and download points to the magnetometer via
RS-232 connection. The operator then simply performs the survey using
the way points as their survey guide. This capability decreases survey
errors, improves efficiency, and ensures more rapid survey completion.
Dumping and processing
effectiveness is also a critical
consideration today. Historically, up to 60% of an operator's "free"
time can be spent on low-return tasks, such as data dumping. Data
dumping times are now significantly reduced through GEM’s implementation
of high-speed, digital data links (up to 115 kBaud). This functionality
is faciliated through a new RISC processor as well as the new GSM-19
data acquisition / display software. This software serves as a
bi-directional RS-232 terminal. It also has integrated processing
functionality to streamline key processing steps, including diurnal data
reduction. This software is provided free to all GSM-19 customers and
regular updates are available.
Navigation and Lane Guidance
The figure on the left shows the Automatic Grid (UTM, Local Grid,
and Rotated Grid). With the Rotated Grid, you can apply an arbitrary
origin of your own definition. Then, the coordinates are always in
reference to axes parallel to the grid. In short, your grid determines
the map, and not the NS direction. The Local Grid is a scaled down,
local version of the UTM system, and is based on your own defined
origin. It allows you to use smaller numbers or ones that are most
relevant to your survey. The figure below shows how
programmable-waypoints can be used to plan surveys on a point-by-point
basis. Initially, you define waypoints and enter them via PC or the
keyboard. In the field, the unit guides you to each point. While walking
between waypoints, lane guidance keeps you within a lane of predefined
width using arrows (< - or - >) to indicate left or right. Within the
lane, the display uses horizontal bars (- -) to show your relative
position in the lane. The display also shows the distance (in meters) to
the next waypoint.
Adding Value through Options
When evaluating the GSM-19 as a solution for your geophysical
application, we recommend considering the complete range of options
described below. These options can be added at time of original purchase
or later to expand capabilities as your needs change or grow. Our
approach with options is to provide you with an expandable set of
GSM-19G Gradiometer Option
Walking Magnetometer / Gradiometer
Fast Magnetometer / Gradiometer
VLF (3 channel)
GPS (built-in and external)
The GSM-19 gradiometer is a versatile, entry level system that can be
upgraded to a full-featured "Walking" unit (model GSM-19WG) in future.
The GSM-19G configuration comprises two sensors and a "Standard" console
that reads data to a maximum of 1 reading every three seconds.
An important GSM-19 design feature is that its gradiometer sensors
measure the two magnetic fields concurrently to avoid any
temporal variations that could distort gradiometer readings.
Other features, such as single-button data recording, are
included for operator ease-of-use.
GSM-19W / WG "Walking" Magnetometer / Gradiometer Option
The GSM-19 was the first magnetometer to incorporate the innovative
"Walking" option which enables the acquisition of nearly continuous data
on survey lines. Since its introduction, the GSM-19W / GSM-19WG have
become one of the most popular magnetic instruments in the world.
Similar to an airborne survey in principle, the system records data at
discrete time intervals (up to 2 readings per second) as the instrument
is carried along the line. At each survey picket (fiducial), the
operator touches a designated key. The system automatically assigns a
picket coordinate to the reading and linearly interpolates the
coordinates of all intervening readings (following survey completion
during post-processing). A main benefit is that the high sample density
improves definition of geologic structures and other targets (UXO,
archeological relics, drums, etc.). It also increases survey efficiency
because the operator can record data almost continuously. Another
productivity feature is the instantaneous recording of data at pickets.
This is a basic difference between the “Walking” version and the GSM-19
/ GSM-19G (the “Standard” mode version which requires 3 seconds to
obtain a reading each time the measurement key is pressed).
GSM-19F / FG "Fast" Magnetometer / Gradiometer Option
The "Fast" version reads up to 5 readings per second. (Sensors
and console are the same as other models.) This system is ideal for
vehicle-borne surveys, such as UXO, archeological or some mineral
exploration applications, where very high productivity is required.
GSM-19 "Hands-Free" Backpack Option
The "Walking" Magnetometer and Gradiometer can be configured with an
optional backpack-supported sensor. The backpack is uniquely constructed
- permitting measurement of total field or gradient with both hands
free. This option provides greater versatility and flexibility, which is
particularly valuable for high-productivity surveys or in rough terrain.
GSM-19GV "VLF" Option
With its omnidirectional VLF option, up to 3 stations of VLF data can be
acquired without orienting. Moreover, the operator is able to record
both magnetic and VLF data with a single stroke on the keypad.
3rd Party Software - A One-Stop Solution for Your Potential Field Needs
As part of its complete solution approach, Terraplus offers a selection
of proven software packages. These packages let you take data from the
field and quality control stage right through to final map preparation
Geophysical Data Processing and Analysis from Geosoft Inc.
GSM-19 with internal GPS board. Small receiver attaches above
Choose from the following packages:
Version 6 -- New Milestones in
Contouring and 3D Surface Mapping
Geophysical Data Processing and Analysis
Semi-Automated Magnetic Modeling
Visualization and Modeling / Inversion
The recent release of v6.0 of the GSM-19 system provides many examples
of the ways in which we continue to advance magnetics technologies for
Enhanced data quality:
Improved operational efficiency:
25% improvement in sensitivity (new frequency counting algorithm)
new intelligent spike-free algorithms (in comparison with other
manufacturers, the GSM-19 does not apply smoothing or filtering to
achieve high data quality)
Enhanced positioning (GPS engine with optional integrated / external
GPS and real-time navigationl)
16 times increase in memory to 32 Mbytes (optional). 4 Mbytes standard
1000 times improvement in processing and display speed (RISC
microprocessor with 32-bit data bus) 2 times faster digital data
link (115 kBaud through RS-232)
More About the Overhauser System
Battery conservation and survey flexibility (base station scheduling
option with 3 modes - daily, flexible and immediate start)
Survey pre-planning (up to 1000 programmable waypoints that can be
entered directly or downloaded from PC for greater efficiency)
Efficient GPS synchronization of field and base units to Universal
Cost saving with firmware upgrades that deliver new capabilities via
In a standard Proton magnetometer
, current is passed
through a coil wound around a sensor containing a hydrogenrich fluid.
The auxiliary field created by the coil (>100 Gauss) polarizes the
protons in the liquid to a higher thermal equilibrium. When the current,
and hence the field, is terminated, polarized protons precess in the
Earth's field and decay exponentially until they return to steady state.
This process generates precession signals that can be measured as
use a more efficient method that combines
electronproton coupling and an electron-rich liquid (containing unbound
electrons in a solvent containing a free radical). An RF magnetic field
-- that corresponds to a specific energy level transition -- stimulates
the unbound electrons. Instead of releasing this energy as emitted
radiation, the unbound electrons transfer it to the protons in the
solvent. The resulting polarization is much larger, leading to stronger
precession signals. Both Overhauser and proton precession, measure the
scalar value of the magnetic field based on the proportionality of
precession frequency and magnetic flux density (which is linear and
known to a high degree of accuracy). Measurement quality is also
calculated using signal amplitude and its decay characteristics. Values
are averaged over the sampling period and recorded. With minor
modifications (i.e. addition of a small auxiliary magnetic flux density
while polarizing), it can also be adapted for high sensitivity readings
in fields less than 20,000 nT (ex. for equatorial work).
GPS - Positioning You for Effective Decision Making
The use of Global Positioning Satellite (GPS) technology is
increasing in earth science disciplines due to the ability to make
better decisions in locating and following up on anomalies, and in
improving survey cost effectiveness and time management.
Examples of applications include:
Surveying in remote locations with no grid system (for example, in the
high Arctic for diamond exploration)
High resolution exploration mapping
High productivity ferrous ordnance (UXO) detection
Ground portable magnetic and gradient surveying for environmental and
Base station monitoring for observing diurnal magnetic activity and
disturbances with integrated GPS time
The GSM-19 addresses customer requests for GPS and high-resolution
Differential GPS (DGPS) through both the industry’s only built-in GPS
(as well as external GPS).
Built-in GPS offers many advantages such as minimizing weight and
removing bulky components that can be damaged through normal surveying.
The following table summarizes GPS options.
Key System Components
Key components that differentiate the GSM-19 from other systems on the
market include the sensor and data acquisition console. Specifications
for components are provided on the right side of this page.
Overhauser sensors represent a proprietary innovation that combines
advances in electronics design and quantum magnetometer chemistry.
Electronically, the detection assembly includes dual pick-up coils
connected in series opposition to suppress far-source electrical
interference, such as atmospheric noise. Chemically, the sensor head
houses a proprietary hydrogen-rich liquid solvent with free electrons
(free radicals) added to increase the signal intensity under RF
From a physical perspective, the sensor is a small size, light-weight
assembly that houses the Overhauser detection system and fluid. A rugged
plastic housing protects the internal components during operation and
All sensor components are designed from carefully screened non-magnetic
materials to assist in maximization of signal-to-noise. Heading errors
are also minimized by ensuring that there are no magnetic inclusions or
other defects that could result in variable readings for different
orientations of the sensor.
Optional omni-directional sensors are available for operating in regions
where the magnetic field is near-horizontal (i.e. equatorial regions).
These sensors maximize signal strength regardless of field direction.
Data Acquisition Console Technology
Console technology comprises an external keypad / display
interface with internal firmware for frequency counting, system control
and data storage / retrieval. For operator convenience, the display
provides both monochrome text as well as real-time profile data with an
easy to use interactive menu for performing all survey functions.
The firmware provides the convenience of upgrades over the Internet via
its software. The benefit is that instrumentation can be enhanced with
the latest technology without returning the system to us -- resulting in
both timely implementation of updates and reduced shipping / servicing
< 0.015 nT / √Hz
+/- 0.1 nT
10,000 to 120,000 nT
> 10,000 nT/m
60, 3, 2, 1, 0.5, 0.2 sec
-40C to +55C
Coordinates, time, date and reading stored automatically at minimum
3 second interval.
Time, date and reading stored at 3 to 60 second intervals.
Optional remote control using RS-232 interface.
Input / Output:
RS-232 or analog (optional) output using 6-pin weatherproof
Storage - 4Mbytes (# of Readings)
223 x 69 x 240 mm
175 x 75mm diameter cylinder
Sensor and Staff Assembly:
GSM-19 console, GEMLinkW software, batteries, harness, charger, sensor
with cable, RS-232 cable, staff, instruction manual and shipping case.
Up to 3 stations
between 15 to 30.0 kHz
Vertical in-phase and out-ofphase
components as % of total field. 2
relative components of the horizontal field.
0.1% of toal field