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With over 2,500,000 lkm of survey data collected in 41 countries particularly on the African continent and Middle East, the Xplorer™ system sets the industry standard for high resolution helicopter-borne magnetic and radiometric survey.


Helicopter Magnetics and Radiometrics

XPlorer™ gradiometer systems utilise dedicated low-noise aircraft, non-magnetic composite horizontal-boom mountings, high speed synchronous data sampling and gradient sensor configurations.

Employing dedicated powerful ASTAR B-series helicopters as a platform, XPlorer™ systems are able to maintain a tight drape with low survey height essential for collecting quality high resolution data. The Xplorer™ system has proven robust and delivered consistently.


Aeromagnetic data is used routinely in most exploration environments to provide essential lithological and structural mapping. Mineralisation is often hosted in complex geological environments and projects benefit significantly from collection of high resolution magnetic data. As magnetic anomalies decay exponentially with distance from source, low survey height is a key component to data quality and encourages the use of helicopter platforms which are also ideal in environments with rugged topography.

Low survey height results in a dramatic improvement in high frequency content:

  • More structural and textural information
  • Better gradient enhancement
  • Improved anomaly definition

Gradient enhanced products improve:

  • Spatial positioning of anomalies
  • Resolution of line parallel features
  • Overall resolution – equivalent to flying at tighter line spacing

High speed data sampling of magnetic (20 Hz) and DGPS (10 Hz) data improves:

  • Definition of short-wavelength anomalies


Aerial gamma-ray surveying reflects geochemical variations of potassium, uranium and thorium in the upper 30 cm of the Earth’s surface. Radiometric surveying thus provides a powerful and cost effective means of mapping outcropping and subcropping geology. In addition to basic lithological information, radiometric data is used directly to map alteration zones (e.g. porphyry copper and shear zone hosted gold); identify surficial extent of uranium mineralisation; and prioritise and discriminate Fe-oxide-Cu-Au, granophile deposits and mafic targets.

Legislation requiring radiation pollution monitoring for the mining industry is becoming a standard in many countries. This is an ideal application for ultra-high resolution radiometric survey.

As part of the XPlorer™ package, NRG™ offers high resolution, full-spectrum radiometric data as a complement to its industry-leading gradient enhanced magnetic data. The reduced survey height offered by a helicopter platform significantly improves signal to noise ratio; which in turn enables a higher sampling rate of 2 Hz (which can be further increased for ultra-high resolution survey). This, coupled with slower survey speed, results in a down-line sample window of approximately 20 m which is a three-fold improvement on standard fixed-wing systems. Up to 2048 in³ NaI crystal pack is employed with full spectrum recorded using industry-leading Radiation Solutions spectrometers. Full spectral NASVD processing is applied to all data as a standard.


Custom designed and built, the NRG™ data acquisition system is at the core of the XPlorer™ system. Synchronous, high speed sampling (> 1,000 Hz) is controlled using a Rb atomic clock. The high sample rates allow for intelligent down-sampling of magnetic data to a 20 Hz base frequency which results in an extremely low noise envelope. Similarly, sample rates of ancillary and GPS data are increased. Flight steering and real-time QC is achieved through a GUI interface for safe pilot-only operation.


Technical Specifications

Magnetic Gradiometer Platform
Type Horizontal Gradient
Sensor Separation 13m
Typical Gradient Noise envelope 0.001nT/m SDEV 4th diff
Aircraft Type AS350B Series
Engine Type Turbine
Fuel Type JetA1
Acquisition System
CPU Dual Core ARM 1.5Ghz
Operation Temperature -10 to 65 Degrees C
Standard Sampling Rate 20 Hz (capable of >1kHz)
Magnetometer Counter
Internal System Noise <0.0001 nT
Adc Inputs 24
Magnetometer Inputs 4
Recording Rate 20 Hz (capable of >1kHz)
Magnetometer Sensor
Type Scintrex CS3
Measurement Range 15 000 – 105 000 nT
Gradient Tolerance 40 000 nT/m
Operating Temperature -40 to +50 Degrees C
Recording Rate 20 Hz (capable of >1kHz)
Fluxgate Magnetometer
Type Bartington
Analogue output +- 10 V
Linearity error <0.0015%
Calibration accuracy +- 0.5%
Bandwidth 0.3 KHz
Internal noise <6 pTrms/Hz @1Hz
Recording Rate 20 Hz (capable of >1kHz)
Base Station Magnetometer
Manufacturer NRG Engineering
Range 15 000 to 105 000nT
Sensitivity 0.0006 nT vHz RMS
Recording Rate 1Hz
GPS Positioning
Type Novatel DL-V3L1L2
Differential Correction Real Time
Code Tracked C/A
Number of Satellites 12
Recording Rate 20 Hz
Gamma-Ray Spectrometer
Type Radiation Solutions – RSX4
Spectral Analysis Real Time
Channels 1024
Data Recorded 256 channel full spectrum
Measurement Range 0 – 3.0 MeV
Dead Time Zero
Recording Rate 2 Hz
Energy Resolution <8.5%
Trigger External
Radiometric Detector
Type Sodium Iodide
Volume 16.7 litres
Stabilisation Automatic
Recording Rate 2 Hz
Type Vaisala
Pressure Resolution 0.001 mb
Operating Pressure Range 600 – 1060 mb
Recording Rate 20 Hz (capable of >1kHz)
Type Vaisala
Resolution 0.05 DegC
Accuracy 0.1 DegC
Recording Rate 20 Hz (capable of >1kHz)
Radar Altimeter
Type Free Flight
Operating range 0 - 762 m
Accuracy 0 - 10 m +-0.3m
Accuracy 10 - 762 m +-0.5m
Recording Rate 20 Hz (capable of >1kHz)
Laser Altimeter
Type SF-01
Range 0 – 60 m
Resolution 1cm
Recording Rate 20 Hz (capable of >1kHz)
Field Data Verification System
Processing Software Platforms Geosoft Oasis Montaj and Proprietary Software