02nT Faster cycle rates Up to 10Hz Longer range detection Pros brPage 5br Magnetometers Magnetometers Large distant targets mask small local targets Difficult to pick out small target due to background noise No sense of direction of target on single ID: 24657
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Gradiometers for UXO Gradiometers for UXO DetectionDetectionAlan Cameron GSE Rentals Traditional Detection Traditional Detection MethodsMethods ..Pulse Induced Metal Detector Towed Magnetometer MagnetometersMagnetometersHigher sensitivity (theoretically 0.02nT)Faster cycle rates (Up to 10Hz)Longer range detectionPros Perhaps 500kg of ferrous materialRelatively large targetRange which gives a 1 nT deflection Range which gives a 5 nT deflection Perhaps 120kg of ferrous materialRelatively large targetRange which gives a 1 nT deflection Range which gives a 5 nT deflection UXOUXO .the targets.the targets what are we looking what are we looking for?for? Perhaps 400g of ferrous materialvery small targetAt 1 nT deflection the range is only 2.9m Range which gives a 5 nT deflection UXO .the targets.the targets what are we looking what are we looking for?for? Current Technology AvailableCurrent Technology AvailableHigher sensitivity magnetometer sensorsLow noise digital transmission.fixed height and accurate line spacing.3D software modelling tools such as Geosoft Oasis montaj.Towed Gradiometer Platforms. Vertical Gradient One sensor mounted Transverse Gradient Sensors mounted side Longitudinal Gradient One sensor behind Total Field Gradient A gradient derived That was the theory, in practice That was the theory, in practice however we need to consider however we need to consider the followingthe followingAttitude of the array must remain stable.A rigid frame must resist vibration.As far as practical keep a fixed altitude.offsets from one another.Frame gives high drag which makes deep towing tricky. GSE Rentals Gradiometer GSE Rentals Gradiometer Acquisition SoftwareAcquisition SoftwareReal time scrolling display.Logs raw sensor data as well as calculated gradient values.Synchronisation of the Overhauser Sensors.Flexible interfacing capabilities. Some obvious things to Some obvious things to consider when planning the consider when planning the surveysurvey ..What is the water depth and the seabed topography like?What vessel can you use? Is it magnetic away?Is the survey location in a difficult magnetic environment i.e. a harbour or near a platform? 18/11/2005Thank you