From the magazine

Understanding utility location tools

Originally, locators relied on the tried-and-trusted electromagnetic field (EMF) technology for locating. Today, this method is still the quickest and generally still the most accurate way of locating underground utility assets. With its trusty transmitter and receiver, an EMF unit can find just about every conductive service with good accuracy in many types of soil conditions.

EMF units have a selection of frequencies to suit the intended location and are able to locate to Class B quality when using the AS5488 Standard. A good locator will also be able to determine signal quality, accuracy and position using different connection methods.

There are many types of locators, but units with multiple frequencies, peak, null, depth and current measurement are the norm for professional locators who rely on these extra features to locate accurately. Of course, an operator needs to have a certain amount of experience to truly understand their machine and use it correctly.

GPR locators

Another great technology that can make a locators life a little easier is ground-penetrating radar (GRP). Although more expensive than traditional locators, GRP has some distinct advantages, such as being able to locate both conductive and non-conductive (such as plastic or Asbestos) pipes in the right conditions. It also works well in congested areas with fewer issues than a more traditional EMF locator.

It is tempting to assume that a GPR, with its functionality in detecting both non-metallic and metallic services, means an EMF locator unit is not required. The problem is, however, that a lot of Australia’s soil types are not conducive to GRP technology – even shallow services can be missed with GPR technology.

Further, GPR technology is only suitable to Class C using AS5488. This is due to a GPR unit not physically connecting to services, as well as a fair degree of knowledge about how GPR works being required for the correct interpretation of a GPR signal.

Other technologies: PWGs and traceable rods and sondes

Other utility locating technologies include pulse wave generators (PWGs), ultrasonic locators, and traceable rods and sondes.

PWGs pulse a pressurised pipe producing signals that can be located using either acoustic or seismic receivers. Whilst PWGs are relatively cheap, they are only suitable for pressurised water pipes and will not give any depth data. Additionally, PWGs are less accurate in positioning compared to EMF and GPR technology. However, they will work in any type of soil condition.

Traceable rods and sondes, meanwhile, are a relatively cheap way of locating non-metallic, non-pressurised services like telecommunication and fibre conduits, along with sewer and other types of non-conductive services using EMF technology.

Recently, a few new technologies such as ultrasonic locators have entered the fray. Ultrasonic locators use sound reflection and work in a similar fashion to GPR technology. Capable of working in all types of soil conditions, ultrasonic locators also have some disadvantages, such as locating voids that may not be pipes.

Like any technology, however, if used in the right conditions, ultrasonic locators will allow a professional locator contractor to locate services that traditionally may not have been detectable with other technologies.

Know your tech

For companies that often rely on the services of professional locator contractors, be aware that there is no holy grail of locator technology. There are many professional locator contractors that will have many tools to achieve good results and these professionals should be able to provide advice on what type of technologies will work and where.

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