A cost-effective GIS alternative for small pipeline operating companies
Current data and methods
Data
Alignment sheet pipeline and facility data now resides in a database connected to the CAD
application. Pipeline data is contained in a master CAD file instead of individual alignment
sheets.
Methods
Alignment sheet data maintenance is performed via the master CAD file and connected
databases. Alignment sheets are generated on an as-needed basis.
Field data access is available through a variety of data viewing applications.
Pipeline asset data is available company-wide via the company Intranet.
Data acquisition and integration process
Data acquisition
Aerial Photography
Monochromatic aerial photography was acquired along PPL IEC’s pipeline route in April
2001. The route was flown 6000 feet above ground level, producing a photo scale of
1"=1000'. Flightlines were laid out prior to flying to ensure capture of a minimum corridor
of 250 yards on either side of the centerline of the pipe.
For a portion of the pipeline, Sewall acquired monochromatic aerial photography at an
altitude of 3960 feet above ground for 1”=660' (1:7,920) scale photography. This
photography was used for mapping along proposed pipeline construction corridors.
Sewall used inertial measurement unit (IMU) and airborne GPS technology to provide high
accuracy data for digital orthophoto production.
Ground Control
Sewall surveyors placed ground control targets and captured target coordinates in order to
provide mapping that meets National Map Accuracy Standards (NMAS) and American
Society of Photogrammetry and Remote Sensing (ASPRS) Class 1 accuracy standards,
suitable for engineering-grade contour mapping. Control GPS technology was used to
acquire control point coordinates.
Pipeline locating
PPL IEC field crews used GPS units to capture coordinates of above-ground pipeline
features. These features included valve stems, casing vents, and road crossings. PPL IEC
provided this data to Sewall in ASCII file format for Sewall’s integration with other pipeline
data sources. The Pennsylvania South State Plane coordinate system was selected due to the
area covered by the PPL pipeline and the opportunities for direct integration of data from
local, state, and federal agencies.
Digital orthophoto production
Sewall first scanned the film to a 1' pixel. After producing the digital terrain model on
softcopy workstations, Sewall produced the digital orthophotos from the digital terrain
model, scanned imagery, photocenter data, and the camera calibration report. Digital
orthophotos were then written to CD-ROM in a TIF/TFW format.
Limited planimetric mapping
Sewall provided limited planimetric mapping consisting of roads and bridges, rivers and
streams, and railroads. Vector mapping was captured to 250 yards on either side of the
pipeline at a 1"=200' mapping scale. For the areas photographed at 1"=660'photo scale,
Sewall produced 2-foot contour topographic mapping. This contour data will be used for
planning, engineering, and construction for new proposed pipelines.
Data Integration
Sewall first merged and spliced the existing CAD alignment sheets to form a continuous
pipeline file. Next, the pipeline was geopostioned and adjusted based on field-collected GPS
data. Sewall then captured pipeline objects and object attribute data using data collection
tools. Captured objects included:
Casings
Cathodic Protection
Coatings
Detail Callouts
Ells/Horizontal Field Bends
Encroachment Data
MAOP
Match Lines
Offline Point Data (Iron Pin, Monument, PK Nail, Drain, Stone, Property Corner, Fence
Corner, Pole, Manhole, Foreign Utility, Road Centerlines, Bridges)
PI Data
Pipe Segments
Property Data
Revisions
Sheet Boundary and Title Block Data
Tees
Thrust/Stabilizer Blocks
Transition Sleeves
Valves
Sewall worked with PPL IEC to resolve apparent data conflicts that emerged during the data
integration process. Identified possible data conflicts were highlighted and transmitted to
PPL IEC. After receiving the conflict resolution , Sewall made the appropriate changes to
the CAD/database data.
Since prior alignment sheets had ROW data and annotations placed according to the
enlarged aerial images, Sewall warped this data to conform to the new digital orthophoto
images.
In order to efficiently place images as backdrops in the new alignment sheet map windows,
Sewall cropped the TIF/TFW images along the placed alignment sheet boundaries. Because
PPL IEC’s field crews expect to find pipeline data on certain alignment sheets, the alignment
sheet boundaries were locked, preventing typical system users from repositioning them.
During the data conversion process, a variety of manual and automated processes were used
to provide quality control on the converted data. Also, Sewall built data validation rules to
check converted data at the time it was entered into the system. The data validation rules
provided conversion technicians with an instant feedback mechanism during data
conversion.
