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Earth Explorer is an online source of news, expertise and applied knowledge for resource explorers and earth scientists. Sponsored by Geosoft.


News & Views

News Archive

December 7, 2016

Geosoft introduces IP and resistivity inversion in VOXI Earth Modelling

Geosoft has added induced polarization and resistivity data inversion to its VOXI Earth Modelling 3D inversion software service. Geoscientists are now able to create detailed 3D models of conductivity and chargeability from IP and resistivity survey data with VOXI. The resulting models can assist in interpreting and targeting regions for mineral and environmental applications...

December 5, 2016

Mexico's Deepwater Round Exceeds Expectations

Some of the world's biggest oil companies showed up Dec. 5 and agreed to invest on the Mexican side of the Gulf of Mexico, proving that deepwater exploration still has a pulse despite challenging market conditions...

November 30, 2016

Magnetic inversion results for Ngamiland available for download

A regional-scale geophysical inversion of magnetic field data in the Ngamiland region of northwestern Botswana is now available for download from the Botswana Geoscience Portal, a partnership initiative of the Botswana Geoscience Institute, industry sponsors and Geosoft...

November 30, 2016

LIGO Resumes Search for Gravitational Waves

After a series of upgrades, the twin detectors of LIGO, the Laser Interferometer Gravitational-wave Observatory, have turned back on and resumed their search for ripples in the fabric of space and time known as gravitational waves. LIGO transitioned from their engineering test runs to full science observations at 8 a.m. Pacific Standard Time on November 30...

November 9, 2016

International Volcano Scientists Unite

For the first time, the United States will host the international Volcano Observatory Best Practices workshop, previously held only in Italy. The workshop will take place this month in Vancouver, Washington. It is designed specifically for volcano observatories around the world and their staff to exchange ideas and best practices with each other...

October 4, 2016

USGS Assesses Mineral Potential for Sagebrush Habitats in Six Western States

USGS has completed a comprehensive assessment and inventory of potential mineral resources covering approximately 10 million acres of Federal and adjacent lands in Idaho, Montana, Nevada, Oregon, Utah and Wyoming...

October 3, 2016

Uganda Targets Up to U.S.$100 Million for Mineral Exploration

Uganda is well endowed with mineral resources and, like many naturally-gifted African countries, is becoming keen on ensuring that these resources play a transformative role in its long-term structural transformation dream - the Vision 2040...

September 9, 2016

Small-Scale Fishers Get A Big Boost With First-Of-Its Kind Impact Investment Fund

Conservation organization Rare announces the Meloy Fund for Small-Scale Fisheries at Our Ocean Conference. The Global Environment Facility, one of the largest funders of conservation worldwide, will be investing $6 million into the fund...

September 1, 2016

Scientists take to the skies to track West African pollution

Scientists operating research aircraft over West Africa have detected organic materials in the atmosphere over a number of urban areas, contributing to concerns of the rise in pollution across the region...

August 17, 2016

New IGS Xplore prospectivity maps for Botswana

International Geoscience Services have released a series of base metal prospectivity maps for the Ngamiland District of northwestern Botswana using free geodata available on the recently-launched Botswana Geoscience Portal, hosted by Geosoft. The maps identify favorable areas for copper, zinc and lead mineralization using geological, geochemical and geophysical datasets downloaded directly from the portal.

August 11, 2016

NexGen Makes New High Grade Discovery

NexGen Energy reported the discovery of a new high grade zone of mineralization 4.7 km northeast of the Arrow Deposit as part of an on-going summer drilling program on its 100% owned, Rook I property, Athabasca Basin, Saskatchewan...

August 10, 2016

Rampion UXO Disposal to Take Place This Week

E.ON has confirmed that the two unexploded devices, detected along the Rampion offshore cable route will be safely disposed this week following the consultation with the Marine Management Organisation...

August 9, 2016

Diamonds In The Rough: E&Ps Find New Reserves In Mature Basins

The oil industry’s history demonstrates clearly that new plays and prospects have long been found in mature basins that were thought to be well on the way to being squeezed dry. Through the acquisition of new data, developing new concepts and coming up with fresh interpretations, long-producing basins around the world from the North Sea to Malaysia have continued to reveal new riches...

August 8, 2016

Northern Shield Identifies High Quality VTEM Targets at Séquoi

Northern Shield Resources announced the results of the interpretation and modelling of the VTEM survey from the Séquoi Property in the Labrador Trough of Quebec . Séquoi is owned 100% by Northern Shield and is being explored for Noril'sk style Ni-Cu-PGE massive sulphides. After geophysical modelling and interpretation of the VTEM data from Séquoi, six VTEM anomalies of significant interest have been identified...

August 3, 2016

Rio Tinto tailors big data drive to copper

Rio Tinto will put the weight of an exploration big data push and its newly-formed Growth and Innovation group behind its desire to identify a "tier 1" copper asset. Speaking at the annual Diggers & Dealers conference in Kalgoorlie, Growth and Innovation group executive Stephen McIntosh said Australia was "overdue for a tier 1" mineral discovery of any type...

August 1, 2016

Tetra Tech Awarded $200 Million Navy CLEAN Contract

Tetra Tech announced that it has been awarded a $200 million, single-award contract by Naval Facilities Engineering Command (NAVFAC) Atlantic. Through the Comprehensive Long-term Environmental Action Navy (CLEAN) contract, Tetra Tech will provide environmental engineering support services to installations within the NAVFAC Atlantic Area of Responsibility...

May 3, 2016

NATO Science for Peace and Security (SPS), MODUM Partners announce "Young Scientist Summer School on Sea Dumped Chemical Weapons"

This international project cooperates closely with CHEMSEA (Search and Assessment of Chemical Weapons) Project for and sharing and knowledge transfer...

April 12, 2016

Monday mad rush for gold stocks

Renewed optimism about the outlook for gold saw investors pile back into gold stocks, pushing many stock to 52-week highs in heavy volumes...

April 11, 2016

Medgold Resources: Continues to Expand the Boticas Gold Project, Portugal; Proposes $200,000 Private Placement

Medgold Resources is pleased to announce new assay results from contiguous rock-chip sampling from the Limarinho South zone at its Boticas gold project in Portugal, which include a highlight of 6.0m @ 5.7 g/t Au...

April 8, 2016

De-carbonizing our energy sector

Nuclear energy currently provides around 11 percent of the world's electricity. China, the European Union, the United States, India, Russia, South Korea, and other nations’ have major existing fleets...

April 1, 2016

Follow-Up Drilling Results Indicate Wide Gold Zones at Hendricks Gold Discovery

Gascoyne Resources Limited announced that it has received the final assay results from the 10,000 metre aircore exploration drilling programme...

March 26, 2016

The Oil Market Is Finally Hitting Its Breaking Point

After a significant reduction in investments over the past two years, oil companies can no longer overcome the production declines from legacy wells...

March 15, 2016

N-Sea Expands into the French Offshore Wind Industry

Subsea IMR provider, N-Sea, has signed a letter of intent with CERES Recherches & Expertise Sous-Marine and TechSub Industrie Environement, to provide subsea survey, installation and remediation services to the French offshore wind industry...

March 9, 2016

PDAC 2016 Convention Exceeds 22,000 Attendees

Optimism and opportunity abounded at the PDAC 2016 Convention of The Prospectors & Developers Association of Canada in spite of recent industry challenges...

March 3, 2016

6 Alpha Launches EOD Contracting Division

6 Alpha Associates, a specialist risk consultancy practice, with expertise in the assessment and management of unexploded ordnance, has launched a dedicated explosive ordnance disposal division...

AUV Magnetometers a leap forward in seabed surveying

An Autonomous Underwater Vehicle-towed magnetometer proves itself in rough weather. The technique could reduce costs and time to complete seabed surveys, with improved accuracies.

by Graham Chandler on March 8, 2013 technology

Use of Autonomous Underwater Vehicle-towed magnetometers could reduce costs and time to complete seabed surveys, with improved accuracies.

"We collected 10-metre survey lines. It travelled at 2.5 knots, and spent so little time in turnaround. It is more efficient than a boat that is going maybe twice its speed."
-Doug Hrvoic

When Doug Hrvoic and his team were out on Lake Ontario to test a new AUV-magnetometer combination last September, they got a surprise bonus. An unexpected storm came up, allowing the unit to prove its utility for survey when the weather turns rough.

Hrvoic is president and owner of Marine Magnetics Corp in Markham, Ontario, a company which specializes in researching, developing and manufacturing marine magnetometers. He’s working in partnership with Massachusetts-based AUV manufacturer OceanServer Technology Inc in an innovative approach to seabed surveys. The idea was to tow a small efficient magnetometer closely behind an AUV—the thinking was it should reduce the need for weather-dependent traditional boat-towed magnetometer arrays. Other devices, for example naval applications and emergency recovery floats, had been successfully deployed behind AUVs but it was first thought that electromagnetic interference would preclude their use as magnetometer tow vehicles.

But it was worth experimenting. “It’s not a thing you’d normally do—you usually would get a lot of magnetic interference,” says Hrvoic. As well, Marine Magnetics’s Explorer magnetometer had been designed for towing behind a boat, so some adjustments first had to be made such as modifying the housing. “We customized the magnetometer to make it neutrally buoyant and other things that you don’t do for a normal marine survey,” he says. “Normally it’s designed to be heavy so it sinks. Also we added some balancing weights so we could adjust trim to make it an easy load behind the AUV.”

OceanServer’s Iver2 AUV model was chosen for its design. “The Iver2 was designed to enable the integration of various sensors by a third party, and without direct involvement of the Iver developers,” says Bob Anderson, president of OceanServer Technology. “From a hardware standpoint, one approach has been to tow a sensor in the water column behind the AUV, and to connect a tow cable/electrical interface cable to a rugged, waterproof connector on the back of the Iver antenna mast.” That connector provides power and a serial communications port to the vehicle CPU he says. “Once the standard Explorer magnetometer was connected, it was a minor effort to provide the limited control interface and to log the data from the magnetometer.”

With the hydrodynamics and connectivity challenges taken care of, the crucial question of electromagnetic interference came next: the towing distance was just five metres aft of the AUV. So the next step would be to collect data under real conditions. “I had a really good data set that we could use to truth and check the quality of the data from behind the AUV,” says Hrvoic. “And also the magnitude of the error that the AUV might be creating, if any.”  Hrvoic’s data set was from the bed of Lake Ontario, which was an ideal testing ground because of its extensive non-magnetic sediment cover, making for magnetic gradients on a smooth geological background. Man-made objects show very clearly against it. Thus any error in the magnetometer data should show up precisely.

The schedule for serious testing had been arranged in advance but the late summer storm was unexpected. “I had [the AUV] shipped here for the weekend and we all had to converge at one spot,” recalls Hrvoic. “Friday afternoon I was watching the weather and could see it could turn bad.” So they decided to get a head start on the testing. It was 7 o’clock in the evening and winds were picking up but still only around 20 km/ph. The rain had started but conditions didn’t appear too bad so they went out to their survey block near the Scarborough Bluffs marina. Soon it turned rougher. Waves were coming off the shore in all directions but they persevered and launched the AUV. Communicating with it from the bridge of their 28-foot survey vessel, they sent it off on its first mission in darkness. Its survey pattern was pre-programmed so the team returned to the dock while the AUV combination did its work three metres below the surface, including data sensing from its Klein side scan sonar which would be used to supplement the mag data.

“The survey block would take five or six hours, broken up into one-hour sections,” says Hrvoic. “We didn’t want it to go too far without checking on it so we came back after an hour and it was where it was supposed to be.” By then the weather service had issued a strong wind warning, waves were hitting two metres in heavy rain, and thunderstorms had moved in, “so it was getting to the point where I didn’t feel comfortable being out any more.” They retrieved the AUV and magnetometer at a pre-programmed pickup point, which they found easy despite the storm. “I thought it would be hard to get close and we would be banging around,” recalls Hrvoic. “But literally to get this thing out of the water the engineer just reached down with one hand and hauled it out—completely painlessly. That was a worry working in rough weather.”

Pre-programming was a definite plus, and Hrvoic says an added advantage of the Iver2 is its Iridium satellite system option, which they didn’t have for the test. “The satellite system allows you to send and receive messages from the AUV,” he says. “If we had that we could get feedback in from onshore letting us know everything is fine and then we could send a message to it to proceed.”

After processing the magnetometer data with Oasis montaj, the team was impressed. “The images are pretty phenomenal,” says Hrvoic. “Extremely sharp.” A number of targets they located were truthed with the OceanServer Mosaic side scan data as well as their existing set. He says because the survey area was close to a marina, there was a lot of junk around—some of it natural and some man-made—but “the mag picture clearly identified things that were man-made and those that were not.”

[Click to enlarge]

Iver2-collected Explorer magnetometer dataset, showing two large steel water intake pipes over a smooth regional gradient background. The survey track is shown as a solid black line. The uniformity of the regional gradient illustrates the high accuracy of the data, showing no signs of heading shifts or motion induced error. Several small magnetic targets are clearly visible and can be correlated with the simultaneously collected side scan sonar data. For example, the anomaly at around 641475E 4839125N is visible in the side scan record as a small partially buried anchor.

Hrvoic likes the accuracy and maneuverability of the Iver2 platform. “We collected 10-metre survey lines,” he says. “It travelled at 2.5 knots, and spent so little time in turnaround. It is more efficient than a boat that is going maybe twice its speed. The survey lines it collected and the altitude it maintained were perfect. When you tow survey lines with a boat you are going left and right and kind of snaking along. This thing collected perfect survey lines under pretty bad conditions—where I would never survey with a boat.”

And the convenience is unsurpassed when compared with boat tow. “All we did was check every hour and then push the button to send it on its next mission,” he says. “And downloaded the data every hour.” That can be relaxed too: the Iver2’s endurance is eight hours and it can store a whole eight hours of data. “You could set it up in the morning and retrieve it in the evening. Or the opposite. Come back when you wake up in the morning.”

A major selling point he figures is that the AUV data set is far better quality than they had recorded in the area with the earlier boat tow. “It blew away my expectations,” he says. “I thought there would be a bit more error with the AUV but it was just the opposite.”

Hrvoic sees no reason why AUV-towed couldn’t eventually dominate over traditional boat towed systems. “In the end it’s cheaper and you don’t have to worry about weather, a major consideration with a boat towed survey,” he says. “And the quality of the data is really a leap forward over any kind of boat towed method. There’s no human being that can drive a boat the way an AUV can drive itself.”Which, although the resolution is the same, vastly reduces errors caused by erratic positioning and noise levels. And that in turn reduces data processing times. “Because there was so little error it didn’t take that much to do the processing,” he says. “We had to do the regular steps like lag correction and diurnial as with any mag survey. It’s the method-caused error that’s being reduced.”

Anderson agrees survey accuracy is a major factor in using the AUV, along with reduced costs.“An AUV system, which includes a mission planning GUI such as the OceanServer VectorMap software program, can predictably follow a defined sub-sea course that covers the area of interest at the optimum track spacing, height from bottom and speed over the bottom,” he says. “Once launched, the operator is free to review previously collected data or to plan future missions. Towing a device with a boat requires more on-site equipment, two skilled operators, and constant attention to safely maintaining the proper positioning of the towfish.”

The combination will be especially useful in marine UXO detection, figures Hrvoic. “It is all boat towed surveys right now and you need very high resolution, which is more difficult with boat survey because you need tighter survey lines and to be more precise when driving.” In UXO surveys for the extensive wind farms in the North Sea for example, operations are continually curtailed due to rough and windy conditions—as these areas are typically chosen for their high wind exposure. He also sees AUVs as useful for anyone doing surveys in shallow waters, i.e. 100 metres or less; often archaeological surveys are in this range.

Hrvoic says R & D on the system is now complete. “This is a product now,” he says. Together with OceanServer Technology, “we are promoting it as a leap forward in surveying.”

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