pdf

High Resolution
Airborne Magnetometer Surveys


High resolution airborne magnetometer surveys can play an important part in your exploration program.  Improvements in magnetometer design have resulted in more accurate data which combined with GPS, yield significantly better aeromagnetic maps.  The overall improvement in accuracy often warrants resurveying areas which were flown using instrumentation and methods now considered obsolete.

High resolution aeromagnetic maps reflect the underlying geology regardless of the degree of exposure in the map area.  These maps are invaluable for exploration in offshore, desert or rainforest environments.  Moreover, they play such an important role in interpreting structures and rock type distribution that high resolution magnetometer surveying can truly be called a basic, universal exploration tool.  The relatively low cost of aerial magnetometer surveys makes them particularly attractive in the early stage of an exploration project, when large areas need to be covered rapidly.

Sander Geophysics Limited (SGL) of Ottawa, Canada, specializes in flying high resolution magnetometer surveys worldwide.  To maintain our position as a leader in the field, SGL's engineers and scientists are actively involved in developing better instruments and survey methods.

Cessna Grand Caravan at the head office

We use optically pumped cesium magnetometers with a sensitivity of 0.005 nT, and computer-controlled real-time digital compensation, giving an overall system resolution of 0.01 nT.  The magnetometer sensors in the aircraft and in the ground station are identical, ensuring that all magnetometer data sets are equivalent in terms of sensitivity and noise envelope.  Sampling rate can be adjusted from 2 to 10 Hz depending on survey specifications.

Good navigation and accurate flight path recovery are very important considerations for high resolution airborne magnetometer surveying.  SGL's aircraft are equipped with Global Positioning System (GPS) receivers integrated into a proprietary navigation and flight path recovery system.  This system, called SGNav, allows for excellent navigation providing an accuracy of better than 1 m in post-flight recovery.

SGNav is used in conjunction with our pre-planned, computer-aided drape flying system, SGDrape.  This system allows us to produce a drape flying surface which is optimal for safety and data quality.  It ensures that adjacent flight lines and control lines are flown at comparable levels, resulting in better quality magnetic data.

SGL's ground stations automatically record diurnal fluctuations of the earth's magnetic field.  Data are recorded on computer hard disk and can be used for correction of the flight data.  Both airborne and ground magnetometer data acquisition computers use a temperature compensated quartz crystal oscillator and a counting circuit to provide real-time clocks.  These clocks are synchronized to the GPS time strobe, which has an absolute accuracy of 0.5 x 10-6 s.

The company´s computing center in Ottawa is equipped for processing and interpretation of high resolution magnetic data.  An array of products designed to represent the geology as expressed through the magnetic data is available.  SGL provides complete interpretational services by experienced geoscientists, enhancing the value of your high resolution airborne magnetic survey.


Airborne Magnetometer Survey System

Airborne Instruments
Magnetometer Sensor Geometrics
Strap-down, optically pumped, cesium split beam
Sensitivity:  0.005 nT
Sensor noise level:  <0.02 nT
Sampling rate:  10 Hz
Compensator Sander Geophysics - AIRComp real-time digital compensation
Range:  20,000 to 200,000 nT
Resolution:  0.001 nT
Sampling rate:  160 Hz
Data Acquisition System Sander Geophysics - SGDAS airborne computer
Capable of recording unlimited number of channels at variable intervals, and digital scrolling chart display of the data.  Data is recorded on a vibration tolerant removable drive.  The system clock is a quartz time standard automatically synchronized to UTC by the GPS signal to an accuracy of 1 millisecond.
Video Imaging System Sander Geophysics - SGDIS digital video
Radar Altimeter   Resolution (m) Calibrated to Range
(m)
TRT AHV8 0.5 1% 0 to 3,050 (10,000 ft)
King KRA-10 0.1 1% 0 to 760 (2,500 ft)
FreeFlight 0.5 1% 0 to 760 (2,500 ft)
Barometric Altimeter Sander Geophysics Digitally Recording Barometric Altimeter 2.0 ±4 m 0 to 10,000 (30,000 ft)
Ground Station Instruments
Magnetometer Sensor Same as airborne
Magnetometer Interface Sander Geophysics - SGRef
Range:  20,000 to 100,000 nT
Resolution:  0.01 nT
Sampling rate:  2 Hz
Data Acquisition System Sander Geophysics - SGRef
This system runs SGL data acquisition software capable of recording an unlimited number of channels at variable intervals, and includes a digital scrolling chart display of the data.   Data is recorded on a vibration tolerant removable drive.  The system clock is a quartz time standard automatically synchronized to UTC by the GPS signal to an accuracy of 1 millisecond.
Power Source 12 VDC can be wind or solar powered
Navigation Instruments
Global Positioning System NovAtel 24-channel, dual frequency, GPS receiver, (ground & airborne)
Sampling rate:  1 to 10 Hz
Real-Time Differential GPS (if required) Satellite link (OmniStar or LandSTAR) to the aircraft for real-time in-flight differential GPS (RDGPS)