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Can you find utilities with just a wand? Passive Locating Scans

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The utility locating process is an essential part of any construction project that involves digging or excavation work. Locating underground utilities like gas, water, and sewer lines is crucial to avoid damage and prevent potential safety hazards. 

One of the most effective methods used by utility locators is passive locating scans. In this article, we will explore what passive locating scans are and how they are used in the utility locating industry.

What is Passive Locating?

Geoscope Utility locator using passive locating scan to locate underground utilities.
Utility locator holding the wand to locate underground utilities on-site

Passive locating is a method of detecting and identifying underground utilities by identifying and measuring their electromagnetic fields. 

It works by detecting the magnetic fields naturally emitted by electrical or communication lines, as well as other metal objects buried underground, such as pipes that magnetic fields can bleed onto. 

Passive locating scans do not require any external signal or transmitter to be present, making it an ideal method for identifying utilities that are not able to be directly connected.

How does Passive Locating work?

Geoscope Utility locator using passive locating scan to locate underground utilities.
Certified utility locator showing how passive locating works

Passive locating equipment is designed to detect and analyse the electromagnetic fields generated by buried utilities. 

The equipment is a single receiver, which has a set of antennas arranged strategically to measure fields and currents that are connected to a computer or data logger. 

The receiver is used to detect the electromagnetic signals emitted by the utilities, while the antennas are used to locate the true shape and depth of the field signals.

When the receiver detects an electromagnetic signal, it provides information about the frequency and strength of the signal. The receiver is moved around the area being scanned, and the information gathered is recorded on a data logger or computer. The data can then be analysed to determine the location and depth of the utility with the help of a trained operator. 

Advantages of Passive Locating Scans

Passive locating scans have several advantages over other locating methods. 

Firstly, they do not require any external signal or transmitter, making it easier to locate utilities that are unable to be accessed or directly connected to because they are energised, locked behind doors, or have been abandoned. 

Secondly, passive locating scans can detect multiple utilities simultaneously, making it a time-efficient method of identifying the location of metallic utilities such as copper communications and power cables. 

Passive locating is a non-destructive method of utility locating, which means it does not damage the underground infrastructure.

Advantages of Passive Locating Scans

1. Complements all other locating methods

Using passive locating scan to locate underground utilities service provided by Geoscope
Passive scans utilised in site-work

No utility locating field work is complete without conducting passive locating scans. That is because the passive locating method works hand in hand to give us a complete picture of what we are finding with its advantages but also what it cannot find in passive locating disadvantages. 

2. Safe

Geoscope Utility locator using passive locating scan to locate underground utilities.
Passive scans being a safe method to use in locating without physical contact to underground utilities

Passive locating scans are a safe way to locate buried utilities, as they do not require physical contact with the utility.

3. Quick and efficient

Geoscope Utility locator using passive locating scan to locate underground utilities.
Utility locator was able to quickly locate underground utilties using passive scans

Passive locating scans can be completed quickly and efficiently, allowing utility locators to pass over a site and quickly make deductions from the results to proceed with accurate locating methods.

4. Suitable for a wide range of applications

Passive locating scans can be used to locate a variety of metallic utilities, including electrical, communication, or water pipes, as well as other metallic objects buried underground, such as gas pipelines.

5. Easy to use

Geoscope Utility locator using passive locating scan to locate underground utilities.
Passive scans being easy to use in locating underground utilities

Passive locating using just the receiver and strategic sweeping patterns are easy to use and does not require extensive training or technical knowledge.

6. Portable

Passive locating equipment is portable and can be easily transported to different job sites, making it a convenient option for locating energised assets.

7. Can be used in conjunction with other methods

Passive scans being used in conjunction with GPR in Sydney, service provided by Geoscope
Passive scans utilised to locate underground utilities in conjunction with GPR

Passive locating scans can be used in conjunction with other utility locating methods, such as ground penetrating radar or electromagnetic induction, to provide more accurate results.

If you are interested in availing passive locating scans in conjunction with other utility locating methods such as GPR or Ground Penetrating Radar, please feel free to click the link below to learn more.

Passive locating Scans with GPR

For anyone planning excavation, or any construction works that break the ground, Ground Penetrating Radar (GPR) is a non-intrusive and non-destructive method of locating underground utilities.
Geoscope

Now that you know the advantages of passive locating scans, let me give you the limitations of passive scans.

Limitations of Passive Locating Scans

Passive locating scans have some limitations, which means they may not be suitable for all types of utility locating projects. 

The accuracy of passive locating scans is affected by several factors, including the depth of the utility, the type of soil, and the proximity of other utilities. The accuracy can also be affected by external electromagnetic interference, such as radio signals or power lines. 

Additionally, passive locating scans cannot detect non-metallic utilities, such as plastic pipes.

Those are just a few of its limitations, but let me expand more with a list of limitations of passive scanning.

Limitations of Passive Scans

1. Limited to metallic and conductive utilities

Passive locating scans can only detect metallic utilities, such as electrical or communication lines, as well as other metallic objects buried underground, such as pipelines. Non-metallic utilities, such as plastic pipes, cannot be detected using passive locating scans.

2. Affected by soil type

Geoscope Utility locator using passive scan to locate underground utilities in wet soil
Passive scans being affected by soil type in utility locating

The accuracy of passive locating scans can be affected by the type of soil present in the area being scanned. The signal strength and frequency can be absorbed or distorted by different soil types, which may affect the accuracy of the scan.

3. Affected by the depth of utilities

Passive scan utilities in work site being affected by the depth of the utilities
Passive scans being affected by the depth of the utilities

The depth of the utility can also affect the accuracy of passive locating scans. As the depth of the utility increases, the signal strength decreases, which may make it more difficult to detect the utility.

4. Affected by the proximity of other utilities

Geoscope Utility locator using passive locating scan to locate underground utilities in Sydney
Passive scan being affected by proximity of other utilities

The proximity of other utilities can also affect the accuracy of passive locating scans. The signals from different utilities can interfere with each other, which may make it more difficult to accurately detect the utility.

5. Affected by external electromagnetic interference

Passive locating scans can be affected by external electromagnetic interference, such as radio signals or power lines. This can cause false readings or make it more difficult to accurately detect the utility.

6. Limited accuracy

Using passive locating scan to locate underground utilities service provided by Geoscope
GPR was used instead to accurately locate utilities instead of passive scans

The accuracy of passive locating scans is limited compared to other locating methods. The depth of the utility may only be estimated, and the exact location may not be pinpointed accurately.

7. Limited range

The range of passive locating scans is limited, and the signals may not be detectable beyond a certain distance. This may require additional scans to accurately locate the utility.

8. Limited visibility

Geoscope Utility locator using passive locating scan to locate underground utilities.
Passive scans having limitations in terms of visibility

Passive locating scans may not be suitable in areas with limited visibility, such as areas with heavy vegetation or buildings. This may make it more difficult to accurately detect the utility.

9. Equipment limitations

Geoscope Utility locator using passive locating scan to locate underground utilities.
Utility locator at Geoscope using a high-quality passive scan equipment

The accuracy of passive locating scans is also limited by the type of equipment used. Lower-quality equipment may not provide accurate readings, which may affect the accuracy of the scan.

Passive locating scans are a useful and non-destructive method of locating buried utilities, they offer several advantages that make them a useful and cost-effective method of locating buried utilities, but they also do have limitations that may affect their accuracy and usefulness. 

It is important to understand and be aware of the advantages and disadvantages or limitations of passive locating scans in utility locating because it helps you to make informed decisions about which utility locating method is best suited for a particular project, identifies potential errors or inaccuracies in the utility locating process, and most importantly it helps you avoid unnecessary delays, costs, or safety risks that could arise from incomplete or inaccurate utility locating.

Accidental Damage to Underground Services

Accidental or not, damage can cause serious problems to workers and disruption to utility services that can affect customers, the community or maybe half the city of Sydney.
Article

Passive is an important locating method, but more importantly, this step needs to be completed in conjunction with a range of other methods and processes and should not be used by itself.

Passive scans being used in conjunction with other methods of utility locating in Sydney
Passive scans being used in conjunction with other methods of utility locating

Finally, if you require utility locating services for your construction project, it is essential to choose a reliable and experienced provider who can offer a range of locating methods to suit your specific needs.

We highly recommend getting in touch with our team at Geoscope, the most trusted and reliable utility-locating service provider in Sydney. 

If you want to book a job with Geoscope, feel free to contact them via their company number: 1300-750-350 or directly fill out the form below:

Picture of Patricia Cupiado

Patricia Cupiado

Co-Author of this Article

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