With a commitment to precision and safety, our underground surveys provide invaluable data on the location of services such as electricity, sewers, gas and water mains, fibre optics, heating, lighting cables, communication networks and traffic signals. They can also offer insights into below ground conditions and features to support the planning process for development projects, as well as research projects and site investigations.

Our underground utility surveys utilise the very latest Electromagnetic Location (EML) and Ground Penetrating Radar (GPR) technologies, offering a multitude of benefits that go beyond reducing utility strikes and the safeguarding of works and the public. However, there are also several potential constraints that can impact the results of a survey. In this blog we’ll explore the benefits as well as the limitations of each method.

First, let’s look at the advantages of underground surveys. These include:

• Mitigating disruptions and delays to projects that can arise from strikes during excavation works
• Lowering projects costs and risks by avoiding delays
• Improving health and safety by ensuring a safe working environment
• Reducing the need for invasive underground inspections and investigations
• The provision of up-to-date records
• Accelerating project progress through a clear understanding of the location of underground services

Exploring our surveying methods

We employ, as standard, two primary surveying methods: Electromagnetic Location (EML) and Ground Penetrating Radar (GPR).

GPR (Ground Penetrating Radar)

GPR operates by emitting radar pulses into the ground and analysing the reflections to create subsurface images. It can detect objects, identify material changes and locate voids and cracks. The versatility of GPR allows it to locate both metallic and non-metallic underground services without the need for manhole access.

 EML (Electromagnetic Location)

EML goes beyond the capabilities of GPR, by positively identifying, tracing and tracking underground services. It comprises two main components: the transmitter and the receiver. The transmitter creates an electromagnetic field, while the receiver detects and analyses the signals emitted by metallic services. Manhole access is necessary for this method, and a separate transmitter can be clamped onto non-power cables to induce a signal.

Advantages and Limitations

Now let’s take a look at the limitations that each survey method can face.

EML Advantages

• Tracks and traces services
• Identifies specific services
• Detects smaller diameter cables

EML Limitations

• Above ground metallic elements, such as vehicles and metallic fences can affect survey results
• In areas with dense cables, individual cable tracing may be challenging, and we will represent such areas as corridors in the survey output
• Limited to detecting metallic services with induced signals
• May not detect metallic services if they have been severed or no longer have live current
• Requires manhole or valve access
• Cannot provide additional subsurface details
• Can detect up to 3-4 meters, but with reduced accuracy beyond 2 meters.

GPR Advantages

• Detects underground services without a power source
• Identifies both metallic and non-metallic services
• Detects below-surface features like voids and cracks

GPR Limitations

• Above ground metallic elements, such as vehicles and metallic fences can affect survey results
• In areas with dense cables, individual cable tracing may be challenging, and we will represent such areas as corridors in the survey output
• Limited to 1.5m penetration depth
• Ineffective on clay subsurfaces
• Ground properties affect GPR results. Ground types that are most conducive include concrete, asphalt and other dry surfaces.
• Will not work on clay subsurfaces
• Requires smooth, even ground contact for clear data collection

Pre-Survey Requirements

With maximum input we can deliver maximum output. So what does maximum input include? In an ideal world here’s what we need you to provide us with, to ensure an effective survey and to optimise results:

• Topographical Survey: Providing accurate site details and any limitations that may affect the survey
• Outline Plan: An area layout to represent the site boundaries accurately
• Photographs: Visuals of potential survey obstacles like metal fences or dense vegetation
• Site Records: Public records of services and utilities, if available. N.b. these can be obtained by us, but at an additional cost.

With our advanced geographical surveying services, our clients gain invaluable insights into the subsurface of their site, ensuring efficient project planning and execution. Our commitment to accuracy and safety sets us apart, making us the preferred choice for your underground surveying needs.

Keen to know more?

Get in touch to learn more about how we can assist you with our cutting edge technology and our expert team. Discover how we can help you embark on your construction journey with confidence.