G&AI’s Aerial Survey and Mapping Division was responsible for providing design-grade digital topographic mapping and digital orthophotography for the Motiva Oil Refinery (approximately 2,000 acres) located in Port Arthur, Texas. This was part of a $10 billion expansion that now makes this facility the largest producer of gasoline, diesel, and petroleum products in the United States. Motiva facility is owned, as part of a 50/50 partnership, by Saudi Aramco and Royal Dutch Shell. Although URS Corporation served as the overall project manager, Gorrondona was contracted with another of the engineering consultants, Arceneaux & Gates, under contract for this project.
Work included the acquisition of low-altitude color aerial photography (1”=250’ photo scale, 1500’ above ground), analytical aerial triangulation from client-furnished horizontal and vertical ground control (33 points), digital topographic mapping (1”=50’ scale standard with a 1-foot contour interval) delivered in AutoCAD DWG format, and high-resolution color digital orthophotos (1”=50’ scale standard with a 3-inch pixel resolution). It also required the collection of extensive planimetric detail including such features as fencelines, utility poles, drain inlets, manholes, etc. The aerial photography was acquired with a Leica RC30 precision aerial mapping camera and consisted of seven flight strips and more than 100 overlapping exposures. The imagery was then scanned with a Leica DSW500 precision photogrammetric scanner, and the map files and ortho-rectified imagery were produced using both Leica LPS and Boeing Autometric photogrammetric software. All map data was prepared in strict accordance with accepted photogrammetric procedures as published by the American Society for Photogrammetry and Remote Sensing (ASPRS) for Class 1 accuracy standards. These standards require that spot elevations and DTM points have an RMSE no greater than seventeen one-hundredths of a foot.