Airborne magnetic geophysical surveys or aeromagnetic surveys are one of the most commonly employed geophysical survey methods being practiced today. Aeromagnetic surveys are considered a primary and essential survey technology ]and are typically flown in conjunction with other survey technologies.
When choosing an airborne geophysical survey company, take the time to consider the equipment offered. A
typical modern system includes; a data acquisition system, one to three cesium magnetometers plus a variety of secondary geophysical sensors, and a specially modified aircraft
equipped with stingers and pods to isolate the sensors from the noise of
the aircraft. The aircraft are periodically degaussed to remove any magnetic noise buildup.
Reliable data acquisition systems are the cornerstone of any
airborne magnetic survey. The basic function of the data acquisitions
system (DAS) for airborne geophysical surveying is to digitally record
all geophysical, navigation, altitude, temperature and pressure data.
Two commercial DAS are readily available, from Picodas and RMS
Instruments DAARC C500. Consider the following when selecting an advanced geophysical
acquisition system:
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Reall TIme Graphical Display – Is the data viewable in real time?
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Magnetometers – How many mags and in what configuration are they?
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Is the system capable of real time correction, or is post flight correction necessary?
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Is the navigation interface available to all GPS instrumentation?
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Is detailed flight path planning available?
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How many channels of analog recording are there?
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Multiple magnetometer inputs
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Adjustable vertical and horizontal scales
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Data is recorded during aircraft turns
Airborne Surveys are normally flown along a series
of equally spaced parallel flight lines. Fore general reconnaissance
mapping purpose the flight line direction is usually oriented
north-south or east-west depending on the predominant strike of the
known geology. For more specific surveys, such as the definition of
mineral exploration targets, the flight-line direction will be oriented
across the strike to maximize the magnetic signature. (Source; ASO
Journal of Australian Geology and Geophysics.)
The quality of data acquired will vary depending on whether the airborne magnetic survey is a
regional or detailed survey. Regional surveys provide data that is typically of
a lower resolution, as the traverse line spacing is usually greater than
250 meters. Detailed surveys have a narrower traverse line spacing, typically less than
250 meters, providing higher data resolution. Detailed surveys are used as a
means of mineral prospecting for magnetic ores such as kimberlites,
asbestos-bearing ultramafic rocks, and magnetic iron ores. Detailed
surveys are also capable of discriminating between non-metallic and
metallic conductors as well as locating specific basement targets.