Survey/Mapping/GPS: Digital Land-Base Maps for Pipeline Resurveying and Mapping
The rigors of resurveying and mapping an acquired pipeline can be daunting. One company has made its surveying and mapping more profitable by applying mainstream PC-based software, Global Positioning Systems, and digital land-based maps.
By David McGee

It's often the case when purchasing a pipeline that a pipeline company will devote tremendous resources to resurveying and remapping the entire line. The pipeline's existing maps usually don't accurately reflect the current geography; vital data may be missing from maps created years ago, and typically property the pipeline crosses has changed ownership several times. Inaccurate maps and not knowing correct property boundaries can lead to difficult right-of-way and leasing negotiations.
      Facing these challenges, Mid-America Pipeline, Tulsa, Okla., wanted to reduce the expense of resurveying and creating accurate maps. MidAmerica set out to survey and map a 197-mile pipeline purchased through a joint venture. The venture which owns the pipeline is called Rio Grande Pipeline Co.1 An element critical to achieving Rio Grande's goal to survey and map the pipeline in 60 days was the company's application of commercial land-base data provided by Tobin Data Graphics (TDG), San Antonio. As a result of implementing a digital land-base map, Rio Grande is better positioned to respond to government regulations and market conditions that are demanding pipelines be georeferenced. Georeferencing the pipeline with land-base maps As Russ Martin, GIS coordinator at Mid-America explains, using TDG's land-base maps made the 197 mile pipeline mapping project more efficient. "We licensed the base map data to begin georeferencing our pipeline and used the base maps for all of the alignment sheets that we developed for the pipeline. Instead of remapping and drafting our own base map, we relied on TDG's data. We were also able to integrate our survey data with the digital base maps." Commercial land-base maps offer many advantages for anyone wanting to streamline the digital mapping process. TDG integrates many data types into base maps: aerial photography, satellite data, paper maps, and historical and other data. These maps include point, line, and polygon coverage and are available in GIS format-ready for surveying and analysis. The task of converting data from other formats is eliminated.
       Rio Grande utilized three TDG land-base products on the project: {SYMBOL 183 \f "Symbol" \s 13 \h} SuperBase Surveydata (Public Land Survey System) which was developed from original Texas Land System, Carter System, 1:24K USGS topographical sheets, and new orthophotography; {SYMBOL 183 \f "Symbol" \s 13 \h} SuperBase state and county-line data, also developed from 1:24K USGS topographical sheets and new orthophotography.); and {SYMBOL 183 \f "Symbol" \s 13 \h} 1:100K DLG (digital line graphs) culture, including transportation and hydrography.
      Mid-America created its digital maps on a Pentium PC running AutoCAD Release 13 for NT and Softdesk software. Mid-America has future plans to link its AutoCAD installation with Environmental Systems Research Institute products ArcInfo, ArcView, and ArcCAD.

First task: Bringing existing maps up to current standards
Running across West Texas from the Midland/Odessa area, to the El Paso area, the existing 197 mile pipeline Navajo was built in the 1920s, and about 80 percent of the pipeline was replaced in the 1980s. Rio Grande determined the initial task was to update the pipeline's existing maps. According to Martin, "The 1928 mapping did not comply with Current Industry Standards, and a lot of data was missing." Martin remembers, "Much of the line had been out of service for some time. We had to bring the mapping up to current standards that we use. We licensed the land-base maps for the pipeline's route and proceeded to decide on the best approach to begin surveying the pipeline."
      The digitally referenced land-base maps provided some immediate gains in efficiency for the survey crew out in the field. The survey crew initially used the old pipeline maps, and finding section corners proved troublesome. Rio Grande, Martin says, "identified the section corners from the TDG digital land-base maps in the area where the pipeline was supposed to be located. The surveyors then entered the longitude and latitude data describing the section corners as way points in their global positioning system (GPS) units. When the field crew surveyed the pipeline, they knew the approximate area where the corners should be located." The surveyors were then able to find 50 percent of the section corners using this method, which speeded up the process of finding the corners considerably.
      Tim Boudreaux, Mid-America's survey coordinator, adds additional details about the project, particularly how the company improved map accuracy. "We used sub-meter level accuracy and held control by one triangulation station. In our surveying and working with the base maps, we determined that the existing paper-based maps were in error. We were actually a quarter section out from the original mapping on part of the line." As surveying and map development progressed, Rio Grande corrected errors and updated its maps to create a true description of the pipeline's geography as well as to determine section corner locations precisely. "After loading our field work into the digital land-base maps," Boudreaux continues, "we could compare our section corner ties to our existing survey line. We found most section corners in the digital land-base maps were within 50 feet of Tobin's Digital Map Section Corners, with some being out by up to 200 feet." Rio Grande has agreed to convey its survey data on section corners to TDG, so that other companies working in the same area can access more accurate base maps.

Teaming digital base maps with GPS and cultural data
Using digital land-base maps is essential to any survey project, Russ Martin believes. Improvements to the surveying process came from having access to a variety of data, such as longitude/latitude and cultural data. Later, when MidAmerica created its digital maps, the ability to combine different data types with survey data resulted in a more detailed description of the geography.
      "We're finding out you can't just survey a pipeline with a GPS and assume you're going to fit the digital land base grid on an accurate location. You have to tie section corners to the survey line and marry the base-map location with your line location to get the most accurate results. The next company that licenses TDG data describing this area will benefit from our surveying." Integrating culture-data relating to roads, waterways, or structures- into the pipeline maps also proved instrumental to the project due to the remote areas Rio Grande was surveying. When combined with topological data, the culture allowed Rio Grande to better understand the areas it was surveying. "Having access to culture from the land-base maps helped us locate our section corners," Martin adds, "but we can't place a survey line in the digital world just by using the culture alone."

Maps assist with landowner relationships
Having more accurate maps has led to changes in how Rio Grande does business in the areas where the 197 mile pipeline runs. Says Tim Boudreaux, "Looking at the pipeline location based on 1930 ownership records and land-grid maps of 60 years ago, we found the pipeline was one quarter of a mile off from its actual position in some areas. This meant we had to contend with ownership differently. Our updated maps showed us the pipeline was on someone else's property and a portion of the right-of-ways have to be renegotiated. Also, land has changed hands so many times some landowners did not know they had a pipeline on their property-other owners knew they had a pipeline, but they were not aware of an easement on their property. Because our surveying and digital mapping identified the pipeline's more accurate location, we're comfortable with the land information we have developed and mapped and that we’re providing the property owners accurate information."
      Boudreaux summarizes the impact of the land-base maps on company operations. "We're now identifying what pieces of the pipeline we want to use and bring it up to standard operating pressure. We did the remapping because we knew we had problems due to the age of the maps we acquired with the pipeline.

Improving documentation and mapping of pipeline assets
As Mid-America Pipeline's experience shows, doubtless there exists great potential for pipeline companies to attain better documentation and surveying of their pipelines, especially with the cost savings GIS and land-base maps can deliver. For example, gathering lines, which take up oil and gas from wells and route petroleum to other pipelines, are notorious for being inadequately referenced. The flexibility offered by land-base maps can make government filings easier and help with managing requirements such as notifying landowners every two years that a pipeline is on their property. In the end, pipeline companies can achieve a better grasp of their pipeline assets and how they relate to the geography where they are built and operating.

About the Author:
David McGee is a freelance writer specializing in the GeoTechnologies. He may be reached at 415-826-1491.

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