EM conductivity surveys measure ground conductivity by the process of electromagnetic induction. Ground conductivity can be used to detect:
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Buried Foundations
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Buried metal objects
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Cavities, including Sinkholes
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Former landfill sites & associated Leachate plumes
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Geological features
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Land drainage systems
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Mine workings
The principal electromagnetic systems used for site investigation are the Geonics EM 31, EM 34-3 and EM 38 ground conductivity meters or the Geophex GEM-2 SKI system. The systems work on similar principles consisting of a transmitter and receiver coil spaced at a fixed configuration, but use different operating frequencies to provide a range of depth penetration and resolution for different applications. Low frequency EM 34-3 systems can be effective for finding large underground cavities such as caves and mine workings but are rarely applicable for smaller targets. The EM 31 operates at an intermediate frequency and is useful for locating discrete features such as sinkholes, abandoned mineshafts and underground storage tanks (UST's). The high frequency EM 38 system is best for detecting small targets buried at shallow depth, such as chemical waste drums and metal artefacts.
Above : Searching for buried metal artefacts with the EM 38.
The Method
EM survey is a rapid and cost effective technique in comparison to conventional resistivity surveys. A primary electromagnetic field output by the transmitting coil induces a secondary field in the ground. The receiving coil measures the magnitude of the secondary field (quadrature component) and the ratio between primary and secondary fields (in-phase component). Quadrature fields are proportional to ground conductivity, being responsive to bulk changes in lithology, groundwater and ground contamination. The presence of metal produces strong secondary fields, making the in-phase component a useful indicator of the presence of buried metal objects
EM data is typically collected as point readings of ground conductivity and in-phase taken at intervals along a survey grid that has been set out over the site area. The spacing of the grid-lines and reading stations is dependent upon the target size. Generally smaller targets require closer survey lines and denser spaced readings.
Processing and interpreting the collected data:
The site data is recorded on a digital data logger for later downloading to a PC for post-survey processing and interpretation. The most commonly used interpretation procedure is contouring, carried out with specialist interactive software to produce contour plans. The contoured data is analysed in detail by our experts to identify anomalous features relative to the general background. Once identified, the anomalies are correlated with local ground conditions. Survey results are presented as plans tied in to site co-ordinates, in a readily understandable engineering CAD format.
Above : Identifying a concealed landfill on a ground conductivity contour plan.
Example of ground conductivity used to investigate swallow holes:
The appearance of a hole in the middle of a school playing field understandably caused concern to the local education authority who commissioned a survey to investigate the area for further swallow holes in the chalk geology.
The survey was carried out using ground conductivity (EM31). The plot shows the vertical quadrature data collected with a notable high conductivity anomaly present to the right of centre. The results were interpreted as high conductivity occurring where saturated gravels are present over the chalk. It is likely that groundwater within the gravels has moved down to the chalk and is aiding the formation of solution features as this groundwater flow in the gravels.
Above : EM31 Ground Conductivity data showing the location of a buried mineshaft.
Frequently asked questions
Using cutting-edge technologies like electro-magnetics, signal induced threading, and Ground-Penetrating Radar (GPR), our underground utility surveys accurately detect a wide array of buried utilities including metal and plastic pipes, drainage systems, electricity cables, telecoms, and fiber optic cables. The methodology ensures high accuracy without the need for invasive trial holes.
Absolutely, SUMO not only marks the detected utilities on-site but also offers high-quality, color-coded survey drawings. These drawings can include topographic features and a comprehensive record of the utility detection survey, ensuring it meets the client’s needs for future reference or pre-construction design works.
In addition to topographic features, SUMO’s mapping service can include fixed surface utility features such as inspection chambers, valve boxes, and telegraph poles. It can also incorporate key topographic details like building lines, fence lines, kerb lines, street furniture, street names, building names, and house numbers, facilitating easy site location.
Yes, SUMO ensures the utility mapping references the ordnance survey grid and level datum as standard. Additionally, the drawings can be supplied to a specified grid and level datum and can overlay an existing topographical survey, making it a versatile and adaptable service for various project needs.
A topographic land survey is a detailed and precise measurement of the physical features and elevation of a piece of land. It provides a comprehensive map of the land's surface, showing natural and man-made features such as hills, valleys, trees, buildings, roads, and bodies of water. This survey is vital for various purposes, including urban planning, construction, and engineering projects, as it offers a clear understanding of the terrain, helping in the design and development of structures and infrastructure.
The SUMO PAS 128 survey makes use of our expertise and top-quality equipment. The output of a PAS 128 survey will include an AutoCAD drawing including Statutory Plans Collation.
These can then be used to print a combined plot of all the services. Each colour coded with depths and quality levels shown. At SUMO, these plots can be large scale.
Our PAS 128 surveys make use of Ground Penetrating Radar to uncover a full utility map, including electrical cables, fibre optic lines, water pipes, sewage systems and gas lines. We operate our surveys in a manner that is the least invasive as possible while also ensuring nothing is missed as we scope out the site, above the surface and below.
In addition to mapping out utilities, our experienced team can accurately survey the land, creating topographical drawings for use.
When including our state-of-the-art Drone technology, larger areas can be surveyed quickly and economically to give accurate and dependable plans for your future project.
The SUMO Utility Detection product is a quick response service for contractors who need to undertake excavation works with a minimised risk of service strikes. We specialise in underground surveying using top-quality equipment to deliver the best results.
Not only can SUMO let you know what is underground, we do it immediately. Our equipment provides real-time information. When we leave the site, the detected utility survey data will show the recorded data on the ground.
The site markings can be reviewed with your on-site staff at the time of survey if requested.
Ground Penetrating Radar is employed across the site as part of a Utility Detection survey to check all electromagnetically traced systems are present as well as other non-metallic pipes and cables which may not be detectable via Electromagnetic detection. Depending upon your requirements, SUMO can offer a PAS128 survey which may be more suitable for your needs and our staff are happy to advise on this.
In addition to mapping out utilities, our experienced team can accurately survey the land, creating topographical drawings for use.
When including our state-of-the-art Drone technology, larger areas can be surveyed quickly and economically to give accurate and dependable plans for your future project.
Using cutting-edge technologies like electro-magnetics, signal induced threading, and Ground-Penetrating Radar (GPR), our underground utility surveys accurately detect a wide array of buried utilities including metal and plastic pipes, drainage systems, electricity cables, telecoms, and fibre optic cables. The methodology ensures high accuracy without the need for invasive trial holes.
Absolutely, SUMO not only marks the detected utilities on-site but also offers high-quality, colour-coded survey drawings. These drawings can include topographic features and a comprehensive record of the utility detection survey, ensuring it meets the client’s needs for future reference or pre-construction design works.
In addition to marking the utilities and topographic features, SUMO’s mapping service can include fixed surface utility features such as inspection chambers, valve boxes, and telegraph poles. It can also incorporate key topographic details like building lines, fence lines, kerb lines, street furniture, street names, building names, and house numbers, facilitating easy site location.
Yes, SUMO ensures the utility mapping references the ordnance survey grid and level datum as standard. Additionally, the drawings can be supplied to a specified grid and level datum and can overlay an existing topographical survey, making it a versatile and adaptable service for various project needs.
The SUMO Utility Detection product is a quick response service for contractors who need to undertake excavation works with a minimised risk of service strikes. We specialise in underground surveying using top-quality equipment to deliver the best results.
Not only can SUMO let you know what is underground, we do it immediately. Our equipment provides real-time information. When we leave the site, the detected utility survey data will show the recorded data on the ground.
The site markings can be reviewed with your on-site staff at the time of survey if requested.
Ground Penetrating Radar is employed across the site as part of a Utility Detection survey to check all electromagnetically traced systems are present as well as other non-metallic pipes and cables which may not be detectable via Electromagnetic detection. Depending upon your requirements, SUMO can offer a PAS128 survey which may be more suitable for your needs and our staff are happy to advise on this.
In addition to mapping out utilities, our experienced team can accurately survey the land, creating topographical drawings for use.
When including our state-of-the-art Drone technology, larger areas can be surveyed quickly and economically to give accurate and dependable plans for your future project.
Using cutting-edge technologies like electro-magnetics, signal induced threading, and Ground-Penetrating Radar (GPR), our underground utility surveys accurately detect a wide array of buried utilities including metal and plastic pipes, drainage systems, electricity cables, telecoms, and fiber optic cables. The methodology ensures high accuracy without the need for invasive trial holes.
Absolutely, SUMO not only marks the detected utilities on-site but also offers high-quality, color-coded survey drawings. These drawings can include topographic features and a comprehensive record of the utility detection survey, ensuring it meets the client’s needs for future reference or pre-construction design works.
In addition to topographic features, SUMO’s mapping service can include fixed surface utility features such as inspection chambers, valve boxes, and telegraph poles. It can also incorporate key topographic details like building lines, fence lines, kerb lines, street furniture, street names, building names, and house numbers, facilitating easy site location.
Yes, SUMO ensures the utility mapping references the ordnance survey grid and level datum as standard. Additionally, the drawings can be supplied to a specified grid and level datum and can overlay an existing topographical survey, making it a versatile and adaptable service for various project needs.
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Survey Methodologies
Detailed Magnetic Survey
Soil Self-Potential
Electrical Resistivity Tomography (ERT)
Soil Thermal-Resistivity Testing
Electromagnetic Ground Conductivity
Electromagnetic Location (EML)
Ground Penetrating Radar (GPR)
