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:
- Real TIme Graphical Display – Is the data available in real time?
- Magnetometers – How many magnetgometers and in what configuration are they?
- Is the system capable of real time correction, or is post flight correction necessary?
- Is the navigation interface available to all GPS instrumentation?
- Is detailed flight path planning available?
- How many channels of analog recording are there?
- Multiple magnetometer inputs
- Adjustable vertical and horizontal scales
- 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.
Specialists in Airborne Geophysical Surveys
Terraquest was established in 1984 and since then, our dedicated team has flown over 1,500 airborne geophysical surveys using both fixed wing and helicopter platforms. Our professional crews provide significant experience having carried out airborne magnetic surveys, airborne gravity surveys, airborne radiometric surveys, and airborne electromagnetic surveys on five continents.
Our quality data sets have been utilized in the exploration for base and precious metals, kimberlite, hydrocarbons, uranium, rare earth minerals and water. The company has performed exemplary surveys for both small and large exploration groups as well as many government agencies. References can be provided upon request. Visit
www.terraquest.ca.
Ed. GMH