TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe Atlantis ocean bottom seismic (OBS) project collected wide-azimuth seismic data from the deepwater Gulf of Mexico using over 900 autonomous nodes which were planted on and retrieved from the sea floor by remotely operated vehicles (ROVs). Rugged topography posed challenges, with the Sigsbee Escarpment, which crossed the area, having depths that varied from 1,200 m to 2,300 m. The project required precise and highly repeatable navigational data to position the nodes correctly and retrieve them quickly. The navigation technique employed a dual Hydrostatic Acoustic Aided Navigation (HAIN) system for node positioning and retrieval, the first time a HAIN system has been used in a stop-and-go configuration with two ROVs running simultaneously. Detailed bathymetric data provided data needed to position the nodes in relatively flat terrain (a maximum slope of 10 degrees). Additional tools included real-time 3D visualization software to gather ROV position data and GIS seabed gradient maps, contour maps, and shaded relief maps to review node locations. This navigation system proved to be successful in yielding a close relationship between node deployment and recovery positions.

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