Ground Survey Methods
Magnetic, Radiometric, Gravity

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Ground Geophysical Surveys

Are a type of subsurface exploration that uses various instruments to measure the physical properties of the earth’s subsurface. These surveys are used to identify subsurface features such as rock layers, mineral deposits, and groundwater resources. They can also be used to locate buried artifacts, pipelines, and other infrastructure. The data collected during a ground survey is used to create maps and other visual representations of the land, which can be used for planning and decision-making.

All Types Of Geophysical Surveys:

measures the magnetic field of the earth’s subsurface in order to locate magnetic minerals, such as iron ore deposits, and buried infrastructure such as pipelines. The data collected is used to create maps of subsurface magnetic anomalies.

measures the natural gamma radiation emitted by certain elements in the earth’s subsurface. This type of survey is used to locate mineral deposits and to map variations in the distribution of natural radioactive elements in the earth’s crust.

measures the gravitational field of the earth’s subsurface in order to infer the density of subsurface materials. This type of survey is used to locate dense rock formations and mineral deposits, and to map variations in subsurface density.

Other Types Of Geophysical Surveys Include:

  • Seismic Surveys
  • Electromagnetic Surveys
  • Ground Penetrating Radar Surveys
  • Ground Conductivity Surveys
  • Ground Resistivity Surveys

Each type of survey is used to measure different properties of the subsurface and to identify different types of subsurface features, depending on the purpose of the survey.

 

Ground Surveys Method:

The method used in ground magnetic surveys is to measure the magnetic field of the earth’s subsurface. This is typically done using a magnetometer, which is a sensor that measures the strength and direction of the magnetic field. The magnetometer is typically mounted on a vehicle or towed behind a vehicle, and is driven along survey lines to collect data. The data is then used to create maps of subsurface magnetic anomalies, which can indicate the presence of magnetic minerals such as iron ore deposits and buried infrastructure.

The method used in ground radiometric surveys is to measure the natural gamma radiation emitted by certain elements in the earth’s subsurface. This is typically done using a scintillometer, which is a sensor that detects gamma radiation. The scintillometer is typically mounted on a vehicle or towed behind a vehicle, and is driven along survey lines to collect data. The data is then used to create maps of the distribution of natural radioactive elements in the earth’s crust, which can indicate the presence of mineral deposits.

The method used in ground gravity surveys is to measure the gravitational field of the earth’s subsurface in order to infer the density of subsurface materials. This is typically done using a gravimeter, which is a sensor that measures the strength of the gravitational field. The gravimeter is typically mounted on a vehicle or towed behind a vehicle, and is driven along survey lines to collect data. The data is then used to create maps of subsurface density variations, which can indicate the presence of dense rock formations and mineral deposits.

Ground Surveys Used For:

Ground Magnetic, Radiometric, and Gravity Surveys are typically used for different subsurface exploration
and resource management purposes:

These surveys are used to locate magnetic minerals such as iron ore deposits, as well as buried infrastructure such as pipelines. They can also be used to map variations in subsurface magnetic fields, which can be used to infer the geology of the subsurface and to identify areas of potential mineralization.

These surveys are used to locate mineral deposits, such as uranium and other radioactive minerals. They can also be used to map variations in subsurface radioactivity, which can be used to infer the geology of the subsurface and to identify areas of potential mineralization.

These surveys are used to locate dense rock formations, mineral deposits, and subsurface cavities. They can also be used to map variations in subsurface density, which can be used to infer the geology of the subsurface and to identify areas of potential mineralization. They can also be used in hydrogeological studies to identify subsurface water reservoirs.

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In general, data collected from these types of geophysical surveys can be used to create subsurface maps, which can be used for resource exploration and management, infrastructure planning and construction, as well as environmental assessment and remediation.

 

Ground Surveys Instruments:

There are several types of instruments used in Ground Magnetic, Radiometric, and Gravity Surveys, depending on the specific method being used.

The main instrument used in ground magnetic surveys is a magnetometer. There are several types of magnetometer, including proton precession, optically pumped, and fluxgate magnetometer. Each type of magnetometer has its own advantages and disadvantages and is suited for different types of surveys.

The main instrument used in ground radiometric surveys is a scintillometer. There are several types of scintillometer, including sodium iodide, bismuth germanate, and cadmium zinc telluride scintillometer. Each type of scintillometer has its own advantages and disadvantages and is suited for different types of surveys.

The main instrument used in ground gravity surveys is a gravimeter. There are several types of gravimeter, including absolute, relative, and superconducting gravimeter. Each type of gravimeter has its own advantages and disadvantages and is suited for different types of surveys.

Other instruments that can be used in these types of surveys include GPS receivers, total stations, and drones. These instruments are used to navigate the survey lines and to collect data on the location of the survey lines and the instruments.

 

FAQs

The main difference between gravity, magnetic and radiometric surveys lies in the physical properties of the subsurface that they measure and the information they provide.

  • Gravity Surveys: measure the gravitational field of the earth’s subsurface. They are used to infer the density of subsurface materials and to locate dense rock formations and mineral deposits.
  • Magnetic Surveys: measure the magnetic field of the earth’s subsurface. They are used to locate magnetic minerals such as iron ore deposits, and buried infrastructure such as pipelines.
  • Radiometric Surveys: measure the natural gamma radiation emitted by certain elements in the earth’s subsurface. They are used to locate mineral deposits and to map variations in the distribution of natural radioactive elements in the earth’s crust.

Each type of survey provides different information about the subsurface and can be used to identify different types of subsurface features. For example, a gravity survey can be used to identify areas of high density that may indicate the presence of mineral deposits, while a magnetic survey can be used to identify areas of high magnetism that may indicate the presence of iron ore deposits. Radiometric survey is useful to identify areas with radioactive elements. The choice of which type of survey to use depends on the specific information needed and the subsurface features being sought.

 

Gravity, magnetic, and radiometric surveys all have their own limitations:

  • Gravity Surveys: The main limitation of gravity surveys is that they are affected by large-scale variations in subsurface density, such as those caused by the presence of large bodies of water or changes in the density of rock layers. This can make it difficult to distinguish between small-scale variations in density that may indicate the presence of mineral deposits and large-scale variations that may not be of interest. Additionally, gravity surveys are sensitive to the instrument’s and surveyors’ ability to maintain a consistent elevation, and are affected by nearby structures or changes in the terrain.
  • Magnetic Surveys: The main limitation of magnetic surveys is that they are affected by changes in the earth’s magnetic field, such as those caused by solar activity or the presence of large bodies of water. This can make it difficult to distinguish between small-scale variations in magnetic field that may indicate the presence of magnetic minerals and large-scale variations that may not be of interest. Additionally, magnetic surveys can be affected by the presence of magnetic minerals in the surface soils, which can obscure the subsurface magnetic anomalies of interest.
  • Radiometric Surveys: The main limitation of radiometric surveys is that they can only be used to locate mineral deposits that contain naturally radioactive elements. Additionally, natural radiation levels can vary depending on the location and the weather conditions, which can affect the accuracy of the data obtained. Also, the presence of man-made sources of radiation, such as nuclear power plants, can create additional background radiation that can interfere with the survey results.

In general, to overcome the limitation of these surveys, it’s required to use multiple methods and to interpret the data carefully and in a multidisciplinary approach. To increase the accuracy of results, multiple measurements are taken at different locations and combined to create a more complete subsurface picture.

 

The data obtained from gravity, magnetic, and radiometric surveys must be interpreted in order to extract meaningful information about the subsurface. The process of data interpretation typically involves several steps:

  • Data Processing: This step involves cleaning and editing the raw data, removing any errors or outliers, and converting the data into a format that can be easily analyzed.
  • Data Analysis: This step involves identifying patterns and trends in the data that can be used to infer the properties of the subsurface. For example, in a gravity survey, data analysis can be used to identify areas of high or low density that may indicate the presence of mineral deposits or subsurface cavities. Similarly, in magnetic and radiometric survey, data analysis can be used to identify areas of high or low magnetic field or radiation that may indicate the presence of magnetic minerals or radioactive elements.
  • Data Interpretation: This step involves using the results of the data analysis to infer the properties of the subsurface and to identify subsurface features of interest. This can involve creating maps and visualizations of the subsurface and overlaying them with other data, such as geologic maps and aerial photographs, to gain a more complete understanding of the subsurface.
  • Modeling: This step involves creating a numerical model of the subsurface based on the data obtained from the survey. This can be used to further refine the interpretation of the data and to make predictions about the subsurface properties in areas where data is not available.

It’s important to note that the interpretation of the data is not a straightforward process and requires a combination of geological knowledge, geophysics expertise, and experience. In addition, the interpretation of data may change over time as new data is collected and new techniques are developed, making it an ongoing process.