Image Pipelines

3 Apr, 2006 By: Michelle Nicolson

PG&E uses aerial photographs to assess areas surrounding natural gas pipelines and keep citizens safe.

More than 5,500 miles of natural gas pipeline snake across California, the nation's most populous state. Entrusted with the safety of the citizens who work and live nearby, PG&E (Pacific Gas and Electric Company) uses GIS technology to analyze areas surrounding the pipeline and to identify HCAs (high consequence areas) -- that is, areas with high concentrations of residences or structures that could be difficult to evacuate quickly in an emergency, such as hospitals, daycare centers and large office buildings.

Federal regulations require pipeline companies to determine the areas where an incident could impact an HCA and require added integrity evaluations to reduce the risk of an incident. At PG&E, staff members use ESRI's ArcGIS system to map pipelines and the surrounding areas. The GIS includes parcel data, land use data and aerial imagery purchased from AirPhotoUSA, which the pipeline integrity department uses for both maintenance and safety analyses. Even with this data, PG&E staff members found a need for more detailed information. The answer was GlobeXplorer's ImageConnect high-resolution aerial and satellite imagery, which the utility began integrating with ArcGIS last year.

A tractor hits a gas pipeline, just one example of a potential emergency situation.

"We use GlobeXplorer when we need a higher resolution to show specific details," says Chris Warner, manager of pipeline integrity for PG&E. The images in ImageConnect are so specific, Warner explains, that PG&E staff members can count the number of parking spaces outside a building or identify picnic tables and frequently used trails in outdoor recreation areas. PG&E staff members can integrate all this information to assess the number of people and the land use around PG&E's gas transmission pipelines.

This type of detail is a key part of analyzing the areas surrounding the extensive pipeline, a task that PG&E repeats each year. Staff uses GIS data and high-resolution imagery from ImageConnect as well as AirPhotoUSA's PhotoMapper to determine when the population density changes around the pipeline to help create and update HCA assessment plans.

The imagery also helps PG&E improve the spatial accuracy of its pipeline data, Warner says. The level of detail in the images helps staff members view not only the road center lines, but also the edges of the road and sidewalks, so the geographic placement of pipelines can be more accurate.

ImageConnect adds detail to PG&E's mapping of its gas pipeline (red line).

PG&E uses GlobeXplorer's ImageConnect as an extension that brings georeferenced satellite and aerial photos into the PG&E GIS system from GlobeXplorer's online database. Users connect directly to GlobeXplorer's image server through software extensions for ESRI (ArcGIS 3.x, 8.x and 9), MapInfo Professional and Autodesk (Map 3D, Land Desktop, Raster Design, Civil 3D and geo-referenced AutoCAD) projects.

Warner credits high-resolution imagery as a key element in improving the mapping of the PG&E gas pipelines. "A high degree of spatial accuracy and resolution quality is necessary for our GIS professionals' analysis of our system and ability to improve the mapping of our facilities."

About the Author: Michelle Nicolson

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