On the Spot GIS: Geospatial Technologies Make Image-Based Mapping Truly Mobile September 4, 2008Posted by Bahadir Sahin in Calismalar (Studies), English.
Tags: Geographic Information System, GIS, global positioning systems
Companies that earn their money by extracting resources from below the ground have an enormous amount of work to do on the Earth’s surface before they can ever sink a spade or lower a drill bit, and most of that work is simply establishing an accurate picture of what that surface looks like. Technologies converging in the mapping space, such as global positioning systems, portable geospatial hardware, and image compression, are making field mapping considerably easier, and big companies such as Chevron and Enbridge are taking advantage of the benefits.
Not only before exploration and production projects, but on an ongoing basis after pipeline production has begun, oil and gas companies need to continue to create and maintain reliable maps showing natural and man-made features and updates to existing facilities.
Technologies converging in the mapping space, such as global positioning systems, portable geospatial hardware, and image compression, are making field mapping considerably easier, and big companies such as Chevron and Enbridge are taking advantage of the benefits.
Satellite Imagery Ideal for Base Maps
Chevron’s Technical Computing Information Management Group in Houston maintains an Oracle database that supports the wide variety of mapping projects that precede construction of pipelines, drill sites, gas plants, access roads and housing.
Nearly every project requires an exhaustive collection of surface data so that accurate analyses can be made of hydrology, hydrography, vegetative cover, soils, lithology and environmental conditions. Cultural features such as roads, buildings and houses must also be mapped with details relating to their size, condition and construction type. Richard Bosley, a Chevron GIS analyst, says that the information gathered by Chevron’s field crews is used “from the very early stage of scoping the project…all the way up to final as-builts.”
Until a few years ago, the recording of feature locations and collection of attribute data had to be performed manually by Chevron’s survey crews taking written notes. And the construction and maintenance crews of another company, Enbridge Inc., navigated its entire pipeline territory using paper maps. “This was a slow and frustrating process,” says Jason De Leon, a field designer in Enbridge’s Pampa office outside of Amarillo. “Often our field people were given coordinates for their destinations, but were not able to find those coordinates on the paper map. Also, the maps made by the Texas Department of Transportation did not necessarily show all the roads that we have up here. Crews spent a lot of time driving around in circles. You’d get instructions like, ‘Go to the windmill that’s losing one of its blades and turn right, then turn left when you see three cows.’”
Today, both companies do nearly all field mapping and navigation digitally.
Field work usually begins with a high-resolution satellite image. Bosley’s group at Chevron uses QuickBird images from DigitalGlobe of Longmont, Colo. Bosley stores as many as nine QuickBird scenes totaling 200 gigabytes on a portable hard drive and carries it with him to the project area. The 0.6-meter spatial resolution of these digital images makes them ideal base maps compared to vector line maps because surface features and land cover types as small as a manhole cover can readily be identified.
“Imagery is the backdrop for all of the work we do on the ground,” says Bosley.
Making Big Images Work in the Field
But the downside to using the high-resolution images in the field is their enormous file size – about 20 gigabytes each. And multiple images are typically required to map an average project area. Even with an added memory card, a top-of-the-line portable mobile GIS device can’t handle files that large.
Bosley selected the GeoExpress image compression and manipulation software from LizardTech of Seattle because it is capable of shrinking a raster satellite image to five percent of its raw file size without perceptible alteration of pixel values or loss of valuable data content. In addition, GeoExpress offers image clipping, mosaicking and reprojecting tools that accelerate data preparation work prior to heading into the field.
In the field, Bosley hooks the external drive to his laptop computer and uses the GeoExpress software to manipulate and compress the images to suit the needs of the field crews. He usually has the software fuse the scenes into a seamless mosaic, which is accomplished on the fly during the compression process. The output can be saved in a standard file format such as MrSID or JPEG 2000. “The benefit is that you do it all in one process,” he said.
Bosley also uses the software to ‘cookie cut’ small image clips from the large mosaic for members of the crew to use in their assigned portion of the project area.