The paper describes the development and field testing of a mapping system utilizing state-of-theart differential global positioning technology and special processing software to automatically create high accuracy, three-dimensional maps of underground gas-distribution and transmission piping systems. Implementation of this system into everyday utility field activities is expected to provide a number of benefits. These include: 1. Ability to create accurate “as-built” maps of utilities as they are being repaired, maintained or constructed in near real time. 2. Reduction in third-party damage from dig-ins realized from precise, accurate markings of underground lines during “One-Call” system requests. Lines can be located to within 1 inch in both the horizontal and vertical planes with state-of-the-art differential GPS. Lines previously surveyed can be re-marked in a fraction of the time required with conventional locators. 3. Improved response to emergency situations made possible by using the technology to rapidly and precisely locate shut-off valves and other critical system features that may be visually obstructed. 4. Higher levels of quality control through real-time tracking of construction and repair activities (length constructed, fidelity to easement boundaries and depth specifications, etc.) and via internet reporting. 5. Re-establishing missing or damaged signage. The work was carried out by Maurer Technology Inc. under the support of the Gas Technology Institute and Memphis Light, Gas & Water Division, Memphis, TN. The field tests included mapping of an existing gas transmission line and a new 8-inch diameter, polyethylene gas main constructed along a major thoroughfare.
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