Introduction
Magnetometer Surveying is a method of geophysical exploration that is used to measure the magnitude, direction and gradient of the magnetic field at a survey location. A magnetometer survey can be used to determine the type and location of magnetic anomalies that could be associated with buried or subsurface features. The survey measures the magnetic field surrounding the area of interest, which includes magnetic signatures from the Earth’s core and crust, as well as any man-made objects or features in the area. Depending on the type of survey conducted, magnetometer surveys can trace out subsurface features such as underground infrastructure, determine the depth and features of ore bodies, and map out Earth’s crustal features.
Types of Magnetometers
There are two main types of magnetometers used in magnetometer surveys:
Proton Electron Magnetometers. The proton magnetometer works by measuring the density of protons in the earth’s magnetic field; the magnetic field is based on the position of the instrument and is not affected by the geometry of the surveyed area. Proton magnetometers measure the total magnetic field intensity, which includes the Earth’s magnetic field and any man-made magnetic fields present in the survey location.
Cesium Magnetometers. The cesium magnetometer works by measuring the spin of the cesium atom in the Earth’s magnetic field; the field is affected by the geometry of the surveyed area and is not affected by the position of the instrument. Cesium magnetometers can measure the anomaly in the magnetic field; these anomalies are caused by the presence of man-made objects or features embedded in the ground.
Process of Magnetometer Surveying
The process of magnetometer surveying consists of the following steps:
1. Planning. The survey will be designed based on the survey objectives, the size and shape of the survey area, and the desired survey accuracy. The survey design should include the type of magnetometer, number of readings, sampling interval, and other data that will be recorded.
2. Set-up. The magnetometer is set-up at the survey location, taking into consideration the survey objectives, the magnetic field strength in the area, and the survey baselines.
3. Readings. The magnetometer readings are taken at predetermined intervals, recording the magnitude and direction of the magnetic field.
4. Analysis. The data collected is analyzed to identify anomalies in the magnetic field, or other features of interest.
5. Reporting. The results and data from the survey are reported to the client or specific stakeholders and interpreted based on the survey objectives.
Conclusion
Magnetometer surveying is a geophysical method used to explore the Earth’s subsurface. The survey can be used to map out subsurface features, determine the depth of ore bodies, and trace out underground infrastructure. Proton and cesium magnetometers are the two main types of magnetometers used in magnetometer surveying, and the process consists of the following steps: planning, set-up, readings, analysis, and reporting. Magnetometer surveys are used by geoscientists, geophysicists, engineers, and other professionals to explore the subsurface and gather valuable data.
