Doug Hrvoic | McMaster University (original) (raw)
Papers by Doug Hrvoic
Small, low cost Autonomous underwater vehicles (AUVs) provide ideal platforms for shallow water s... more Small, low cost Autonomous underwater vehicles (AUVs) provide ideal platforms for shallow water survey, as they are capable of unmanned navigation and can be programmed to acquire data at constant depth, or constant altitude above the seabed. AUVs can be deployed under most sea states and are unaffected by vessel motions that often degrade sonar and magnetometer data quality. The integration of sonar and magnetometer sensors on AUV’s is challenging, however, due to limited payload and strong magnetic fields produced by the vehicle motor.
In this study, a Marine Magnetics Explorer Overhauser magnetometer was mated to a portable AUV (OceanServer Iver2) creating the first practical AUV- deployed magnetic survey system. To eliminate magnetic interference from the AUV, the magnetometer was tethered to the AUV with a 5 m tow cable, as determined by static and dynamic instrument testing. The results of the magnetic tests are presented, along with field data from a shallow water test area in Lake Ontario near Toronto, Canada. AUV-acquired magnetic survey data were compared directly with a conventional boat-towed magnetic survey of the same area. The AUV magnetic data were of superior quality despite being collected in rough weather conditions that would have made conventional survey impossible. The resulting high-resolution total magnetic intensity and analytic signal maps clearly identify several buried and surface ferrometallic targets that were verified in 500-kHz side- scan sonar imaging and visual inspection by divers.
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SEG
The analytic signal is a well-known magnetic data form that provides a high frequency, symmetric ... more The analytic signal is a well-known magnetic data form that provides a high frequency, symmetric response that is centered over source bodies regardless of the effects of permanent (remnant) magnetization or the inclination of the ambient field. This, and its immunity to the effects of diurnal variation make it an ideal data form when searching for ferrous objects such as pipelines, unexploded ordnance (UXO), mines, or archaeological remains.
A recent marine magnetic site clearance survey conducted by the U.S. Naval Underwater Warfare Center (NUWC), Keyport division, is presented in which SeaQuest, a new 3- axis marine gradiometer was employed. Using highly accurate total-field Overhauser sensors, this gradiometer system simultaneously measures all three components of the total-field magnetic gradient vector, thus allowing the calculation of the 3-D analytic signal in real time. The presented results highlight the advantages of interpreting measured analytic signal data when attempting to quickly locate the position and depth of ferro-metallic objects. The results also demonstrate the gradiometer system’s sharp resolution of small ferro-metallic signatures, particularly in the presence of strong geologically-sourced anomalies.
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Hydro Magazine, Jul 2004
Magnetic surveying is a common methodology for small-object detection applications such as UXO cl... more Magnetic surveying is a common methodology for small-object detection applications such as UXO clearance, pipeline location and archaeology. Now gradiometers using Overhauser technology are doing the job faster and better by directly measuring the analytic signal – a high-resolution data form that is ideal for resolving small magnetic features and eliminating the unwanted effects of geology and solar interference.
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Teaching Documents by Doug Hrvoic
A good introduction to geomagnetism and magnetometers.
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Small, low cost Autonomous underwater vehicles (AUVs) provide ideal platforms for shallow water s... more Small, low cost Autonomous underwater vehicles (AUVs) provide ideal platforms for shallow water survey, as they are capable of unmanned navigation and can be programmed to acquire data at constant depth, or constant altitude above the seabed. AUVs can be deployed under most sea states and are unaffected by vessel motions that often degrade sonar and magnetometer data quality. The integration of sonar and magnetometer sensors on AUV’s is challenging, however, due to limited payload and strong magnetic fields produced by the vehicle motor.
In this study, a Marine Magnetics Explorer Overhauser magnetometer was mated to a portable AUV (OceanServer Iver2) creating the first practical AUV- deployed magnetic survey system. To eliminate magnetic interference from the AUV, the magnetometer was tethered to the AUV with a 5 m tow cable, as determined by static and dynamic instrument testing. The results of the magnetic tests are presented, along with field data from a shallow water test area in Lake Ontario near Toronto, Canada. AUV-acquired magnetic survey data were compared directly with a conventional boat-towed magnetic survey of the same area. The AUV magnetic data were of superior quality despite being collected in rough weather conditions that would have made conventional survey impossible. The resulting high-resolution total magnetic intensity and analytic signal maps clearly identify several buried and surface ferrometallic targets that were verified in 500-kHz side- scan sonar imaging and visual inspection by divers.
Bookmarks Related papers MentionsView impact
SEG
The analytic signal is a well-known magnetic data form that provides a high frequency, symmetric ... more The analytic signal is a well-known magnetic data form that provides a high frequency, symmetric response that is centered over source bodies regardless of the effects of permanent (remnant) magnetization or the inclination of the ambient field. This, and its immunity to the effects of diurnal variation make it an ideal data form when searching for ferrous objects such as pipelines, unexploded ordnance (UXO), mines, or archaeological remains.
A recent marine magnetic site clearance survey conducted by the U.S. Naval Underwater Warfare Center (NUWC), Keyport division, is presented in which SeaQuest, a new 3- axis marine gradiometer was employed. Using highly accurate total-field Overhauser sensors, this gradiometer system simultaneously measures all three components of the total-field magnetic gradient vector, thus allowing the calculation of the 3-D analytic signal in real time. The presented results highlight the advantages of interpreting measured analytic signal data when attempting to quickly locate the position and depth of ferro-metallic objects. The results also demonstrate the gradiometer system’s sharp resolution of small ferro-metallic signatures, particularly in the presence of strong geologically-sourced anomalies.
Bookmarks Related papers MentionsView impact
Hydro Magazine, Jul 2004
Magnetic surveying is a common methodology for small-object detection applications such as UXO cl... more Magnetic surveying is a common methodology for small-object detection applications such as UXO clearance, pipeline location and archaeology. Now gradiometers using Overhauser technology are doing the job faster and better by directly measuring the analytic signal – a high-resolution data form that is ideal for resolving small magnetic features and eliminating the unwanted effects of geology and solar interference.
Bookmarks Related papers MentionsView impact
A good introduction to geomagnetism and magnetometers.
Bookmarks Related papers MentionsView impact