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SeaQuest3-Axis Gradiometer

SeaQuest is the ultimatemagnetic target detectionplatform. It gives you moreinformation, and helps yousee just what you want to see.

The needle in ahaystack finder

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The Overhauser Effect

Marine Magnetics SeaQuest gradiome-ter measures the ambient magnetic fieldusing a specialized branch of nuclearMagnetic Resonance technology, appliedspecifically to hydrogen nuclei.

Highest Absolute Accuracy

SeaQuest has the best ab-solute accuracy of any ma-rine gradiometer: 0.1nT.

High Sensitivity

SeaQuest sensors deliver high-resolutionoutput with a noise level of 0.01nT; coun-ter sensitivity is 0.001nT.

Worldwide Operation WithNo Restrictions

SeaQuest is entirely omni-directional, meaning younever have to orient yoursensor because it is already

optimized to work around the world. As aresult, regardless of where you are in theworld and no matter what the magneticfield strength is, your SeaQuest sensorswill continue to provide a strong signaland accurate data.

Maintenance-Free Sensors,No Realignment and NoConsumable Parts

SeaQuest Overhauser sensors are en-tirely maintenance free and most im-portantly, SeaQuests specifications donot degrade over time. As a result, SeaQuest sensors, unlike optically pumpedsensors, never have to be realigned orrecalibrated in order to meet the manu-facturers specifications at the time oshipping.

Accidents happen. Sea-Quests hard-anodized alu-minum frame is ready forthem, providing strength

and rigidity while keeping weight down.Most of the frame is covered with anultra-tough and flexible composite that

forms the surface area of the wings pro-tects the frame from impact.

All cables are contained within the pres-surized sub-housings, or within the hol-low free-flooded wings. This, coupledwith its sleek, swept design minimizesthe ability to snag foreign objects anddebris. The entire structure is designed todeflect impact rather than absorb it.

The bottom-wing ballast weight keepsSeaQuests center of gravity lower thanthe towing axis, keeping pitching androlling motion to a minimum. The largesurface area of the wings ensures that theplatform will tow straight and smooth,even in high sea states. All this comestogether to produce the highest qualitydata possible in a towed marine gradi-ometer.

SeaQuest 4 Sensor Gradiometer

with Floats and GPS IntegrationThe four-sensor SeaQUEST provideshorizontal, vertical, and longitudinal gradienmeasurements. A floatation sub-assemblykeeps the gradiometer within metres of thewater surface. An on-board GPS receiverenables the system to append a position toeach measurement.

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t u r e s

S t a b i l i t y a n

d D u r a

b i l i t y

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On-Board Sensors

In addition to our Overhauser sensors, accuracyis further improved by the integrated tilt sen-sor. The sensor continuously monitors the tini-est platform movements caused by rough seas,telling the operator exactly how horizontal andvertical the gradient measurements are. Theechosounder/altimeter measures bathymetrywith 0.1m precision, which provides a precisereference for the vertical gradient measure-ment, and allows continuous compensation formagnetic variation caused by igneous bedrock.

Floats

This makes deployment and retrieval very easy,as the vessel can be stopped and the tow bodycan be brought in by hand, with very little re-sistance.

The floats can be adjusted to sit more forwardor aft on SeaQuest, presetting its natural pitchin the water. When the floats are forward, Sea-Quest will remain at the surface at any speed. Inaft positions, the SeaQuest wings act as a de-pressor, causing it to descend to a fixed depthat a fixed speed.

The floats are air-filled, and equipped with pres-sure relief valves. If the floats are damaged andleak under pressure, the valves will allow any in-

ternal pressure to dissipate slowly as SeaQuestis brought to the surface

On-Board GPS

SeaQuests floatation assemcan be equipped with a GPS mWith the system configuredtow up to 1.5m below the sur

SeaQuest will position its gradiometerwith the onboard GPS, providing unmapositioning accuracy. The GPS antenna ineered for marine use, and is fully wateand submersible.

SeaQuest is Ideal For UXO and mine detection Cable and pipeline tracking Environmental survey Archaeology

SeaQuest 7 Sensor Array with Floats

The SeaQuest Array combines seven sensors to provide two setsof horizontal, vertical and longitudinal gradients.

I have been using a complete 2-unitSeaQuest array and have found themagnetic data delivered to be excellent,with less than one nano-tesla of variabilityin the total gradient (analytic signal).

Richard Funk, Geophysicist

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Mapping Marine Ferrous Targets Using theSeaQuest Gradiometer System

The figures on the right show the results of a target survey conductedby the United States Naval Undersea Warfare Center (NUWC) Key-port, WA. The images show the striking contrast between conventionalmagnetometer (total field) data and the high resolution gradient data

obtainable with SeaQuest.FIGURE 1 shows the total magnetic field data collected by the top sen-sor of the SeaQuest platform. This image represents data that wouldbe obtainable by a conventional total field survey and is presented forcomparison purposes. The total field image is dominated by north-south trending curvilinear anomalies, which are likely related to mag-netic susceptibility variations in the bedrock. This strong backgroundmagnetic response makes it difficult to quickly identify anomaliesassociated with ferrous objects. Presenting the total field grid with astretched colour-scale allows identification of at least four potentialferrous targets in the western half of the survey site.

In contrast, the total gradient map (FIGURE 2) allows easy identifica-tion of at least 12 (high-confidence) ferro-magnetic objects withinthe survey block. The wavelengths associated with the geologicalmagnetic effects are effectively suppressed in this image in compari-son to the total field image. Targets are defined by simple bulls-eyetype positive anomalies, which are centered over the target position.In the western part of the survey block, a low amplitude NNW-trend-ing linear anomaly is present. This anomaly corresponds to a knownpipeline marked on the marine charts of the area. It is worth notingthat the amplitude of the pipeline anomaly is less than 0.5nT/m, andyet it is clearly visible in the total gradient map.

Also of interest is the large anomaly east of the center of the map.Despite its size, the anomaly is obscured by geology in the total fielddata, yet it shows up prominently in the total gradient data.

It is easy to see that the total gradient (Analytic Signal) directly mea-sured by SeaQuest provides the clearest results, effectively creatingan intuituve magnetic image of the sea bottom. While the singleaxisgradient results enhance only certain types of anomalies based ontheir geographic direction, the total gradient is effectively a direction-

independent result, enhancing all near-surface anomaliesequally, andsuppressing deep geology evenly.

Magnetic gradient is commonly used to enhance the signals fromsmall, relatively close sources typical of iron manmade objects,and to suppress the signals from large distant sources associatedwith geological variation. The total gradient technique goes evenfurther by eliminating the directional dependence of conventionalgradiometer methods. This produces an easily interpreted magneticimage of the sea floor, with target positions unambiguously markedby bulls-eye type anomalies. Also, the total gradient anomalies are

expressed with a higher signal-to-background-noise ratio thconventional techniques, enabling the identification of tinthat would otherwise be invisible.

The SeaQuest gradiometer platform enables the acquisiton quality total gradient data because of its hydrodynamic stabthe high absolute accuracy of its sensors, producing clean re

from heading errors and offsets. Despite high currents and ing conditions, SeaQuest provided consistent results that diquire the filtering or level-shifting that are necessary steps, sources of calculation error, for other gradiometer instrumen

For a more comprehensive discussion on the threory of total-fieldgradiometry see the detailed case study available for download frowebsite at www.marinemagnetics.com

Figure 3: Interpretation of data products overlaid on grayscale totaent map. Primary target depth estimates (see triangle symbols) obtfrom Euler Deconvolution of the measured gradients. Total gradienvalues of the target position provide an estimate of the relative targ

Figure 1: Total magnetic field map of the NUWC survey site. The image inated by North-South trending curvilinear anomalies related to buried geoOnly a few ferro-magnetic targets are identifiable. The Eastern part of theblock is dominated by geological noise.

Figure 2: Total Magnetic Gradient (analytic signal) map of the NUsurvey site. The deep geological signal is eliminated, and extremesmall targets can be easily resolved, including a faint linear featurthe west that was invisible in the total field data. The linear featurresponds to a known pipeline.

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A Gradiometer Solutionfor AUV & ROV Installations

The only gradiometer that deliversan expandable sensor array withoutcompromise

Worldwide operation, no dead zones No heading error Best absolute accuracy on the market 0.1nT 0.01nT sensitivity; 0.001nT counter sensitivity Ultra low power requirement Sensors do not degrade with time and never need calibra

meet our specs at time of shipping

Features Isolated inputs/outputs/RS232 no ground loops Auxiliary sensors include: 3D compass, tilt sensor, leak

in E/M, pressure sensor, altimeter Sensor distance from another sensor: no restrictions, ie

can even touch Sensor distance from electronics module: 0.25m (10 inc

30m (98 feet) Entirely non magnetic construction. All aluminum and Depth ratings available 300m, 1000m, 3000m, 6000m

Electronics moduleIn Pressurized Housing

RATING LENGTH DIAMETER

300m 12.7" 0.51000m 12.75" 0.53000m 12.25" 0.66000m 12.25" 0.65

SensorIn Pressurized Housing

RATING LENGTH DIAMETER

300m 15.5" 0.51000m 15.5" 0.53000m 15.0" 0.66000m 15.0" 0.65

12.25"

3000m depth rated

6" 6"

15"

Its expandableEach SeaQuest is comprised of a single electronics module that candrive up to 4 sensors. Add as many SeaQuests as you need.

Auto synchronization it just worksMultiple SeaQuests are always synchronized to each other via a sync

line hardwired to each additional electronics module. Synchronizationof SeaQuests is entirely seamless. You can even synchronize by sendingcommunications from the host directly to the gradiometer.

SeaQuest 6 sensor gradiometerwith 2 electronics modules

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info@marinemagnetics.com+1 905 479 9727 | marinemagnetics.com

Features at GlanceWorldwide operationHighest absolute accuracyHigh sensitivityResolutionPower consumptionMaintenance free sensorsNo heading errorNo drift

No temperature dependence

AltimeterHeadingTilt sensorPressure sensor

No restrictions or dead zones0.1nT0.01nT0.001nT2W standby, +1W persensor,+2W per altimNo realignment and no consumable partsEliminates the need to level your dataA complete lack of1/fnoise providing a toflat noise spectrumData accuracy does not change through atemperature range of40C to +60C0-100m range,0.1m step3-axis magnetoresistive compass,0.1 degrTwo-axis,0.1 degree step300m range,0.1m step (others optional)

Specifications

Why SeaQuest?You get more information

SeaQuest measures the gradient in all three axes simultane-ously, so no matter how your heading changes no informationis lost. Horizontal gradiometers, on the other hand, are limited

by the fact that they can only measure the gradient in one axis(direction) at a time. When surveying with a one axis gradi-ometer and your heading changes by even a few degrees youare no longer measuring the same gradient.

Auxiliary sensors include: 3D compass, tilt sensor, leak

detector in E/M, pressure sensor, altimeter Sensor distance from another sensor: no restrictions,

ie sensors can even touch Sensor distance from electronics module: 0.25m (10)

to 30m (98) Entirely non magnetic construction. All aluminum

and fiberglass Depth ratings available 300m, 1000m

See what you want to seeSeaQuest suppresses geology and enhances small nearby targets, enato see more of what you want to see, while suppressing what you donsee. Single-axis gradiometers and arrays enhance targets and geologicawithin the direction of their axis. Since SeaQuest measures the compmensional gradient, it enhances signals from small targets uniformly, retheir geometry or position in space.