Word |
Definition |
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 |
Cable |
A line normally to conduct electricity and so contains metal which can be detected with an electromagnetic locator |
CAD |
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 |
Diffraction |
A GPR term used to describe the ‘hyperbolic’ shape seen in a radargram caused by the reflections from a buried pipe |
Drainage |
A network of pipes and channels to collect both foul and surface water and carry it to an outfall |
Duct |
A pipe (normally relatively small diameter) installed to carry cables or other utilities |
EM |
Electromagnetic – the principle behind the operation of locators |
EML |
Electromagnetic locator |
EOT |
End of trace with a reason why. Other terms such as ‘unable to trace’ (UTT) or ‘signal lost’ (SL) are also used |
EuroGPR |
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 |
Geophysics |
The measurement of physical properties of the ground. Anomalies in the data can be used to determine the position and size of buried features |
GPR |
Ground penetrating radar |
GPS |
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 |
Main |
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 |
Manhole |
An access onto a utility line large enough for man entry. Mainly associated with drainage systems |
Overhead |
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’) |
Pipe |
A conduit mainly used for gases and liquids. Can be made from metallic and non-metallic materials |
Radargram |
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 |
Radiosonde |
A small self-contained device emitting a signal that can be inserted into a conduit and then traced at ground level |
Scar |
A scar on the ground surface indicating where a utility may have been buried. This is often in the form of road surface reinstatement |
Service |
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 |
Trace |
The detection of a signal associated with a utility. It is implied that the line is also marked onto the ground surface |
Transect |
A line or swept width along which a search is carried out – often associated with GPR surveys |
Trench |
A temporary hole dug to visually locate and measure the position of a utility |
Underground |
A term used to describe a buried utility as opposed to overhead |
UTL/UTR |
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. |
