such as the American Petroleum Institute and the Interstate Natural Gas Association, the PIPES Act includes efforts to prevent damage by third parties, i.e., accidental contact with or damage to a buried line. The problem is being addressed from two directions. First, a new technology has emerged that can accurately detect the location depth of buried pipelines. Second, locating technologies can couple with geospatial solutions to produce accurate position information that is tied to known coordinate systems. The resulting survey-quality data forms the basis for GIS-based approaches for planning, asset management, operations, and emergency response. An integrated solution In 2015, surveyors from Woolpert, Inc., a major U.S. architecture, engineering, and geospatial firm, used a SPAR 300 subsurface utility surveying system on a pilot project in northern Ohio. According to Dave Kuxhausen, Woolpert discipline leader for surveying and geomatics, the work was done under a contract to locate underground utility lines on a client’s property. “We used the SPAR unit coupled with Trimble R10 GNSS receivers to detect those lines,” Kuxhausen said. “It wasn’t a large project, but it established our relationship with them and showed that we had the capabilities to perform this type of work.” The SPAR 300 uses magnetic field sensors to determine the distance to a buried pipe or other asset that is capable of carrying an electric current. (The system induces a current into the pipe or tracer wire via connection at a valve or other exposed component.) The SPAR sensors can be integrated with Trimble GNSS receivers or total stations that are connected to Trimble Access software running on a Trimble TSC3 or other field controller. In operation, field crews use the SPAR 300 to locate buried pipes in three dimensions. The Trimble Access display indicates when the SPAR has located a pipe and aids the crew in following the pipe. The system provides horizontal and vertical offsets from the sensor to the pipe while the GNSS receiver supplies precise geographic positioning. When the crew wants to capture a measurement, Trimble Access automatically combines the data from the SPAR and GNSS sensors and stores the resulting positions into its database. In addition to a 3D coordinate on the pipeline itself, the solution also computes coordinates for points on the surface directly above the pipe. In a single pass, the survey crew can detect and mark the pipe as well as capture survey-grade positions. The resulting locations approach the accuracy of Level A excavations (see “Four levels of accuracy and cost”). Kuxhausen said that, depending on the integrity of the tracer wire, the system enables his crews to capture pipe depths accurate to roughly 0.25 feet (8 cm) while working with the speed and flexibility associated with Level B electromagnetic sensors. The field data is transferred to Trimble Business Center (TBC) software. “We run the data through a QA/QC process in TBC,” Kuxhausen said. “Then we export the data into shape files (SHP format) and look at them in an Esri-type environment to check for gaps or overlaps. We take advantage of the fact that the data comes with a depth and a surface elevation. In many instances, we’ll turn it into a profile view to make sure that the depths look consistent down the line and there are no spikes or obvious issues. Then that data is delivered to the client.” New business from underground Kuxhausen said that clients are quick to recognize the value of the integrated technologies. In addition to mapping mandated by the PIPES Act, he is hearing from
Surveyor Ron Siney initiates a location survey with GNSS and the SPAR 300.Wires connected to the gas meter induce a current into the underground pipeline.
Information from the SPAR 300 is shown on the display of the Trimble TSC3 field controller. Operation and output from the locator is integrated into the standard surveying workflow.
Vincent Johnson collects data above a gas pipeline.The system uses GNSS to produce georeferenced location and depth for the buried pipe.
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