Of all the causes, the correct interpretation of equipment remains a key determinant in the accurate detection of underground utilities. Many experienced operatives misread signs, especially at crucial times, which led to costly mistakes. Understanding why false signals happen with Cat & Genny equipment can be the key to preventing cable strikes and enabling safe excavation.
What Causes
a False Signal?
False readings or misleading information usually
occur when the signal generated interacts with multiple buried conductors. In a
busy underground environment, where cables and metallic pipes exist in
clusters, this also happens to be quite frequent. The locator detects multiple
paths or reflections of the signal and may indicate that there is a cable in a
location different from the real one.
Induction can also be confusing when the signal is
taken through the ground rather than directly through the intended conductor.
Nearby metallic objects may re-radiate the signal unintentionally, and this
secondary transmission could create on the receiver's display or via audio
feedback what looks and sounds like a "ghost" line, making it
impossible to determine which way the true cable lies.
Environmental
and Human Factors
Ground conditions play a large part in signal behaviour.
For example, wet soil will improve conductivity and spread the signals wider
than anticipated. Conversely, dry or compacted soil could weaken them and make
utilities more difficult to trace.
Poor scanning techniques are also major contributing
factors. Hurrying the scan, missing sweep patterns, or holding the locator at
the wrong angle can distort results. Even minor conditions such as low battery
power or poor calibration may yield missed or doubled signals.
How to
Minimise Misreads
The first step in any search is proper preparation.
Before switching on the Cat & Genny,
review the site plans and existing service drawings to anticipate what
utilities might be present. Always conduct a full sweep in multiple modes
(Power, Radio, and Genny) to confirm findings from more than one source.
Another important practice is periodic equipment
checks. Calibration ensures sensitivity levels are appropriate and that the
locator is detecting signals uniformly. While scanning, move at a consistent
pace and angle, keeping the locator as close to the ground as possible for
optimal readings.
It is also a good practice to mark and rescan the
detected lines from different directions, as a real utility will keep its path
consistent, while false signals usually fade or shift with movement.
The Bottom
Line
Most misreads can be traced back to either
interference or operator technique. Knowing how signals behave and the
environmental factors that influence them allows operators to interpret
readings with more confidence. The more time spent understanding equipment and
refining a scanning method, the fewer surprises there will be once excavation
starts.
