by Anthony Johnstone, NULCA Committee Assistant and Access Detection Director
A new range of high-quality utility locators has recently been introduced to the market, including the Rycom Pathfinder Professional, RD 8100 and the UT9000/Utili-Guard. While these units are all equipped with the latest features and technology designed to make utility location easier, do they lead to better locating or make an operator a better locator?
New functions
These new units come equipped with innovative multi-function modes which give operators little control over the instrument, these normally include automatic depth, automatic gain and cable directional indicators. Rycom call it ‘Easy Mode’, RD call it ‘Guidance Mode’ and the UT9000 known as ‘left and right guidance’.
The functions work by using a combination of antennas in the receiver which guide the operator to the location of the pipe. In most simple locates (round or clean fields) they are just as accurate as the standard ‘Peak and Null’ mode. However, mistakes can occur if there is any change to the quality of the magnetic field, like distortion as a result of interference from other services, resulting in far less-accurate location.
False sense of accuracy
One brand goes as far as to force the operator to rotate the receiver until an indicator lines up before it will provide depth information. The antenna that uses this function is influenced by the same distortion that can affect the other antennas in your locator, so the operator thinks the service is going in a different direction when it is actual field distortion creating the error.
This is just one example of locators becoming more sophisticated, with many new functions designed to make locating easier, but creating a false sense of accuracy.
An operator should also use caution when using the combined ‘Peak and Null’ modes. These modes normally give the operator more control with the machine, in some cases giving an experienced operator a clear indication if there is field distortion without having to switch between the two standard modes. The reality of the combined modes is, due to the operator not having the correct training, there is a reliance on the left and right guidance arrows normally associated with this mode.
Left and right guidance
The left and right guidance systems relies on the null, or vertical antenna, which is susceptible to field distortion more so than the peak antennas. In a lot of cases the operator uses the mode thinking it is more accurate; however, it can ultimately lead to the same issues as the other multi modes.
Anyone who has ever used these modes on a weak signal will understand that they can flicker and change resulting in false readings. So, although machines are offering a broad range of functions and sophistication, they do little to improve the accuracy of the location and in some cases, processing the additional information, can slow the unit down.
Locators with in-built GPS systems are an example of marketing hype. None of these systems are good enough to use for any kind of mapping, with accuracy of less than 3 m. Any form of mapping requires sub decimetre accuracy usually associated with a separate RTK based GPS system, in a clear environment.
Even then the GPS unit needs to be in line with the blade of your receiver to get the accuracy required. Machines with inbuilt GPS units should only be used for on-board logging, tracks the general location of an operator and, in some systems, logging a machines data and functions.
Worthwhile functions
The functions of a locating machine depend on the type of locating they are performing. Operators in congested areas should favour a unit which performs on low frequencies, equipped with a target direction mode, although these must be used on well-earthed low-resistant services.
Receiver and transmitter communications tools can also be useful, allowing the user to select a frequency or increase the power of the transmitter from the receiver. This feature can be beneficial in a scenario where the operator is more than 100 m away from the transmitter. Units fitted with an accessory port also make the unit more flexible.
Suppliers regularly underestimate the important role that training plays in utility location, with the salesperson in many cases knowing little, if anything, about how the machine operates. A minimum of four hours of training should be mandatory with the purchase of a sophisticated locator.
The selection process
In my time as a trainer, I have seen many examples of operators who have been sold an expensive locator, only to be been shown the basics of the machine, and advised that the simplistic modes are all that is required to perform an accurate location. This is far from the truth and, in the worst case scenario, can result in dangerous mistakes or incorrect markings.
Trials of new units should be completed in a more challenging environment to ascertain whether the machine can perform under the real-world pressures. An operator should always have a good understanding of the technology before paying a fortune for a locator, especially as it might come equipped with functions that are not required. It is also important to buy from a reputable company that specialises in this area, ensuring some form of training is provided or available, and that the instrument can be serviced at an authorised location.
For more information visit the Access Detection website.
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