This page contains a simple glossary of technical terms used in our content. If clarification or further information is needed, feel free to contact us.



 Active mode

A term applied to electromagnetic locator surveying where a signal is directly connected or induced onto a pipe or cable. This term also includes the tracing of accessible pipes and ducts through the insertion of a radiosonde or line threader (see also ‘passive mode’)

 Base mapping

Mapping often supplied by the client at an appropriate scale in vector format onto which the results of the survey can be overlaid


A line normally to conduct electricity and so contains metal which can be detected with an electromagnetic locator


Computer aided design often used to overlay the results of the survey onto base mapping

 CAT & Genny

An acronym for a locator being a ‘cable avoidance tool’ and signal generator


A GPR term used to describe the ‘hyperbolic’ shape seen in a radargram caused by the reflections from a buried pipe


A network of pipes and channels to collect both foul and surface water and carry it to an outfall


A pipe (normally relatively small diameter) installed to carry cables or other utilities


Electromagnetic – the principle behind the operation of locators


Electromagnetic locator


End of trace with a reason why. Other terms such as ‘unable to trace’ (UTT) or ‘signal lost’ (SL) are also used


European GPR association

 Excavation (hand)

A trial pit or trench temporarily dug by hand to expose utilities to confirm their position

 Fibre optic

A telecommunication line using optical fibres for the transmission of data. Unless reinforced the line will not contain metal so is undetectable with an EM locator


The measurement of physical properties of the ground. Anomalies in the data can be used to determine the position and size of buried features


Ground penetrating radar


Global positioning system

 Gravity systems

A drainage system that relies on gravity to convey the water. Access is therefore possible via manholes and can be traced with radiosondes or line tracers

 Inspection chamber

A chamber affording access onto a utility – often too small to allow a person to enter

 Line threading

The use of a rod or radiosonde that emits a signal allowing its route to be detected and traced at ground level


The principal utility conveying liquid, gas, telecommunications or power as part of a distribution or collection system. This would normally lie beneath part of a highway


An access onto a utility line large enough for man entry. Mainly associated with drainage systems


Common usage describing the position of a utility if not buried

 Passive mode

A term applied to electromagnetic locator surveying where passive signals emitted by a pipe (power and radio modes) are detected and traced on the ground (see also ‘active mode’)


A conduit mainly used for gases and liquids. Can be made from metallic and non-metallic materials


The output trace from a GPR unit along a transect. It is made up of a series of individual point scans to form an apparent continuous image


A small self-contained device emitting a signal that can be inserted into a conduit and then traced at ground level


A scar on the ground surface indicating where a utility may have been buried. This is often in the form of road surface reinstatement


The connection from a utility main to a property

 Signal generator

A device used to generate an electromagnetic signal that can be induced or directly connected to a conductor

 Survey (utility)

The process of carrying out the detection location and mapping of buried utilities

 Survey area

The area defined by the client within which the survey is to be carried out


The detection of a signal associated with a utility. It is implied that the line is also marked onto the ground surface


A line or swept width along which a search is carried out – often associated with GPR surveys


A temporary hole dug to visually locate and measure the position of a utility


A term used to describe a buried utility as opposed to overhead


Unable to lift/unable to raise – usually referring to manhole covers etc. Some contractors may also use this to mean ‘unable to locate’, which refers to a lost or buried manhole cover.

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