Utility mapping, typically underground, investigates and determines the general or precise location of buried utility lines such as gas, water, and electrical lines. Global Positioning System (GPS) and Total Station equipment is used to map the location of utility markings, utility structures, underground storage tanks (USTs) and test hole locations. Site conditions and client requirements dictate which system will be employed or if the systems will be used in tandem.
Most often it is the ground composition that influences the engineers’ decision when they determine the most suitable type of technology to use to locate buried pipelines and cables. Some methods will provide a general locus, while others offer more precise locationing. If the client is seeking the most precise positioning, Survey Grade utility depictions in a cad file or on a print typically represent the location of the utility mark out and utility surface features to an accuracy of 1.2”. The utility locating instruments used will typically detect the utilities to plus or minus 1′ (one foot). The surface features will be mapped to 1.2” tolerance horizontally.
For more general locationing, Mapping Grade utility depictions typically are not as precise. These locations are considered approximate. The handheld GPS units used for this type of utility mapping, often state accuracies of 10 meters or roughly 30′. However, depending on soil composition, such as loose sand as compared with packed soil, accuracies can sometimes be obtained to 0.5’ (one half foot) or so.
PULs’ Utility Mapping Equipment
PULs technicians utilize the following equipment to perform utility mapping:
Trimble GeoXH 6000 series with Tornado external antenna – accuracy to 10cm
Trimble R8 GNSS Model 3 Rover
Trimble S6, Robotic Vision and Multitrack