The advent of GIS technology has ushered in a new era for utility companies that require precision data regarding their underground pipeline assets. The importance of obtaining accurate, as-built pipeline information—specifically, precise positional measurements in three dimensions—is clearest in cases when the lines extend beneath congested or inaccessible spaces. Examples include pipelines that run beneath roads or beneath bodies of water. In such cases, pipeline maps may be absent entirely or; even if available, may indicate line locations that vary substantially from the pipelines’ actual locations.

Technology companies have thus sought innovative techniques for securing the required information and for presenting it in a convenient format for their utility clients. One such company is Geospatial Corporation of Sarver, Pennsylvania. Their major innovations include accurate navigation sensors called “probes” that are either pulled through pipelines with the aid of a mule tape or propelled by fluid pressure within the pipe, while collecting precision data that is provided to the client in an easy-to-access format. The details of this technology are reviewed below.

Smart mapping technology
The smart mapping tool technology can provide accurate x, y, z centerline mapping of pipeline infrastructure and seamlessly integrate this open format data into all GIS or CAD databases.

This service maps the pipeline in three dimensions and produces a precise depiction of its plan view and profile. Gyroscope and accelerometer based inertial measurement units within the mapping tool measure angular and linear velocity changes at 800 Hz in the x, y and z axes as the unit moves through the pipeline. The mapping tool can map most pipelines with a high degree of positional accuracy by using reference points with known geographical coordinates at the start and end points of the run and, on very long runs, at known intervals between the two.

The mapping tools are “untethered,” which means that there is no requirement that a communication cable be attached to the mapping tool. This allows greater flexibility in the utilization of the technology. Since these tools are autonomous, all data is stored onboard, and there are no practical length or depth limitations.
Acquired data can be downloaded onto a laptop PC and viewed immediately for evaluation in the field. Digital “plan and profile” sectional drawings of the pipeline are produced, overlaid on the existing plan view of the site, and printed onsite. Additionally, this digital data can be transferred via the Internet to any location in the world to be evaluated by associated decision-makers or stored and entered into the appropriate GIS/CAD database by the program administrator for future reference and use.

This technology allows the economical digital mapping of pipelines as small as 1.5 inches (3.8 cm) to as large as 96 inches (243.84 cm) in diameter. In addition, mapping tools are designed in numerous body styles, some of which permit the negotiation of extremely tight (90 degree) bends. Custom body styles have been developed that are specifically designed for potable water pipelines and others for small fiber optic/telecommunications conduits. The mapping tools are capable of operating in any pipeline medium.

They can locate and digitally map water pipelines, gravity sewers, pressure sewers (force mains), telecommunication conduits, oil and gas distribution pipelines, electric utility conduits, environmental pipelines and most industrial pipelines.

The technology also presents an economical method for creating accurate, “as-built” three-dimensional drawings of new pipelines that are installed utilizing either Horizontal Directional Drilling (HDD) or conventional “open cut” methods. Not only are the “as-built” drawings accurate and quick to produce; they also seamlessly integrate into AutoCAD and most other major GIS databases.

Profile mapping technologies can also provide a detailed “bending radius analysis” of the installed pipeline and detect installation errors that may lead to premature pipeline failure due to over-stressing of the pipeline. By implementing a program that provides several centerline profiles over a fixed period of time, pipeline settling and deflection can be determined.

During rehabilitation programs of gravity sewers, this mapping tool technology can provide not only the invert coordinates of each of the sewer lines, but can economically provide accurate profiles showing any “bellies” or “settling” of the sewer line. These damaged sections can then be rehabilitated via “spot repair” methodologies prior to relining. Again, accurate digital data can be integrated seamlessly with today’s major GIS/CAD databases.

This system has become a key element within the Subsurface Utility Engineering (SUE) methods for projects involving locating, mapping, imaging, and validating pipeline and conduit systems below ground. Geospatial provides all SUE quality levels; records research and GIS baseline development, line locating, GPS surveying, imaging using ground penetrating radar, and validation of asset location using vacuum excavation. By including the system for accurate pipeline mapping, the whole SUE process is significantly improved, offering utility owners and operators greater accuracy, less contingency, and reduced risk of line strikes.

PROBE pipeline mapping and geometry tool

Advances in GIS-related technologies, such as the PROBE pipeline mapping and geometry tool, are enabling gas utilities to obtain precise information on their underground systems.

A pipeline mapping project
Geospatial Corporation was recently contracted by Sunoco Logistics to complete a mapping and centerline geometry survey of two HDD bore crossings for 8-in. pipelines in the northwest Oklahoma City area. Specifically, Sunoco contracted Geospatial to survey its crude oil pipeline system in two locations. Detailing the steps involved in this project can help to convey the value of the mapping tool technology described above.

Geospatial used one of its pipeline mapping tools (DR-HDD 4.2) to provide Sunoco Logistics with a number of items, including: x, y, z positional data of the pipes’ centerlines in a GIS and CAD database file format; a two-dimensional plan and profile view of the pipeline with known surface elevation; and a three-dimensional representation of the plan and profile with known surface elevation. In addition, bend quantification, joint identification, and digital caliper results were provided. This process has now become the standard by which HDD bore crossing as-builts are produced, including direct measurement of installed pipe geometry used for structural integrity assessment.

The value of the work performed is summarized as follows: trenchless installation and rehabilitation of pipes using this mapping process will be validated and as-built plan/profiles [can be] produced, risk and uncertainty of position is eliminated, [and] engineering design and performance analysis can be carried out with confidence, and direct measurement of the bend radius and joint alignment of the installed [or existing] pipe, and detection of any mechanical damage such as dents, wrinkles, or ovality exceeding the pipelines’ design and installation criteria is measured. This provided the most complete and comprehensive record for the installation, and key data for integrity management of the pipeline system.

Specifications of the acquired data
The accuracy of the three-dimensional position data that was obtained corresponded to the operating specifications of the probe. The horizontal relative accuracy was 1:400 and the vertical relative accuracy was 1:1,000. (Technically, He = +/- 0.0025 * d, Ve = +/- 0.0010 * d, where d = the distance from entry to intermediate or exit points along the pipeline.) The resolution of the resulting map is selectable and delivered at one-foot intervals, with a complete feature list that includes x, y, z position; stationing (odometer); and classification (joint, bend).

The mapping tool detected pipe joints, along with any misalignments, to an accuracy of 1.0°. It also identified and quantified bends and the simple deflection angle. The bend segment span was calculated at 2, 20, and 50-ft segments to ensure that both short and long spans were detected. A digital caliper tool was run in tandem with the mapping tool in order to identify any ovality exceeding design criteria. The accuracy and resolution are +/- 0.01-in. Sunoco Logistics provided the detection threshold for reporting of 7.125", which was not exceeded for either pipeline HDD segment.

Elements of the project
Geospatial dispatched a fully equipped two-man survey crew to the work sites in Oklahoma City. They obtained precise GPS coordinates for all entry, exit and update points along the pipeline routes. They also oversaw the installation of a mule tape messenger line to facilitate the progress of the mapping tool through the pipelines.

Meanwhile, Sunoco Logistics secured bonds, permits and access to the job sites and pipe access points. They ensured that the pipelines were clean and clear; provided unobstructed and unconstricted access along their entire length; and possessed an internal diameter that did not exceed +/- 10% of the nominal diameter. They performed hydro testing, ensured that entry and exit points were capable of accommodating Geospatial’s mapping tool, and properly shored and dewatered those access points.

Work process
The Geospatial crew arrived at the work site on the morning of the survey, and participated in the initial operations safety briefing. The pipeline was ready, with open ends for the entry and exit of the mapping tool. Installation of a messenger line was performed by using a simple high-cubic-foot-per-minute leaf blower and parachute, with a subsequent pull-through of a 1,200-pound “mule tape” that served as a lead line for the mapping tool.

Subsequently, the mapping tool was installed in the pipe entry and calibrated for one minute. The lead line was attached to the front of the probe, as well as a lag line at the opposite end. A reel system was then installed at either end of the pipeline in order for the mapping tool to complete one round trip through the line. Each run required between 5 and 15 minutes.

Field processing was then carried out for each round-trip mapping run. This step required approximately 30 minutes to complete, and helped to provide assurance that the results were within performance specifications.

Next, an ENVIROCAL (www.enviro-cal.com) digital caliper was programmed and inserted for the final pass through the pipelines. This system is used to detect geometry defects such as excessive ovality, dents, buckles and wrinkles that may have been accidentally produced during the pull-through of the pipe. The mule tape was subsequently reeled out of the pipeline upon the completion of the survey.

Conclusion
The successful mapping and geometry survey described above highlights the advantages offered by the use of one company’s proprietary technology as well as the presentation of the derived dataset within a GIS framework. While this case study involved pipelines located beneath roads in a high growth zone and expansion of the road system where the technology’s value for mapping lines beneath transportation corridors, waterways, and in more crowded urban areas, is evident. This is a key element in a project design and execution process, such as SUE provides.

Given the importance of accurate as-built information, ease of use of the technology, and the fact that the resulting data becomes part of the overall integrity management of pipelines, it is expected that a growing number of utility companies will come to rely on this type of mapping and analysis strategy in the future. Just as Google Earth has revolutionized how we navigate the surface of our planet, it is anticipated that the growing use of this technology will facilitate the creation of a “Google Underground,” affording similar levels of interactivity and three-dimensional imaging for owners and operators of pipelines.

The author
Todd R. Porter is Executive Vice President – Energy Services & Strategics, Geospatial Holdings, Inc., Sarver, Pennsylvania.