With ever increasingly crowded subsurface the need to know what is running beneath any ground surface has become imperative before considering how to install, repair or renovate buried services and utilities. This has led to the development of digital mapping software which can be interfaced with the output from various mapping and detection technologies. As well as interfacing with GPR and CAT systems output used in general utility mapping surveys (see Radio/Electromagnetic Detection and Ground Penetrating Radar), using GIS (Geographic Information Systems) and GPS it is possible to engage with the data generated using in-pipe mapping systems such as Gyroscopic Mapping technology. Gyroscopic Mapping systems usually comprise a Gyro Compass contained within a wheeled tubular device that is winched or rodded through the pipeline being surveyed.
Winching is used in longer surveys. The device includes an inclinometer and a data recording system. To complete a survey, assuming a winched operation, a winch cable is passed through the pipe over the survey length between accessible access points/manholes. The Mapping unit is attached to the winch at the start position and surveyed accurately to provide a reference starting position and elevation. The unit is then winched through the pipeline. The gyro compass senses any changes in direction and the inclinometer any changes in grade. Distance measure is also taken as the unit advances. This information is recorded on-board (it may be that for shorter surveys the data feed may be direct to the start position via a data cable).
On completion of the survey and knowing the accurately surveyed start point, the changes in direction and grade and the known distance from the start point provide inputs to mapping software or even paper plans to show the linear route between the start and end point in 3 dimensions. This identifies depth below surface at any given distance and sumps or humps along the route that may cause flow disruption. The digital data can be stored for future reference.