Proceedings Of The Marine

SUM 2015

Proceedings magazine is a communication tool for the Coast Guard's Marine Safety & Security Council. Each quarterly magazine focuses on a specific theme of interest to the marine industry.

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Navigation

Page 16 of 70

14 Proceedings Summer 2015 www.uscg.mil/proceedings Other People Collect Good Data, Too Several other agencies and organizations collect high-quality systematic surveys in U.S. waters, using calibrated systems and expert observers. The U.S. Geological Service maps some areas for geological interpretation, Bureau of Ocean Energy Management personnel map areas for wind farm siting, and U.S. Army Corps of Engineers stafers map areas for coastal erosion studies in addition to their work in navigational channels. Additionally, the National Marine Fisheries Service (part of NOAA) surveys fsheries habitat areas. Often these surveys are adequate to update chart bathymetry. However, it is unusual that they are collected in critical under-keel clear- ance areas, highly changeable areas, or in areas where we have identifed discrepancies; in other words, they don't address many priority requirements. However, since these surveys are freely available, we selec- tively choose from among them to update the chart in areas where the survey is good quality and can improve the chart, given the existing charted information and the chart scale. plotters, mobile apps, and dedicated data loggers that are capable of recording depths along a track. While these systems are not calibrated, and often have inad- equate information about draft, sound speed, or tide to be suitable for direct charting, the aggregation of many measurements can be useful for detecting patterns of change. Survey requirements can be classifed into three categories: • Critical under-keel clearance: Small depth changes that affect deep-draft traffc are not detectable using any of the above approaches, and the environmental and economic risk of large ships grounding requires us to ensure there are no shoals or obstructions. This periodically requires systematic surveys in these areas to update the depths and to locate any seafoor obstruc- tions. • Changeable: In highly dynamic navigational depth areas, such as the Louisiana coast, Atlantic inlets, or Alaska's Cook Inlet, we know that our depth observa- tions are highly perishable, and thus require regular updates. • Targeted discrepancies: In other areas, however, we can pursue a strategy of resolving discrepancies from reports, AIS, satellite-derived bathymetry, crowd- sourced bathymetry, and coastline satellite photos. This targeted approach can be compared to a painting touch-up job, where a full survey is the equivalent of completely repainting. In Sum All vessel operators need better data, faster. The technology is emerging, agencies are collaborating, and NOAA has a vision for the future. Our navigation mission is simple — to provide navigation products and information that improve ocean-going commerce and coastal economies, keep peo- ple safe, and protect coastal environments. About the author: Captain Shepard Smith is the National Oceanic and Atmospheric Administration's Offce of Coast Survey deputy hydrographer. Previously he was chief of Coast Survey's Marine Chart Division and senior advisor to the acting NOAA administrator. During his 20-year NOAA career, he spent nine years at sea as a feld hydrographer. He holds an M.S. from the University of New Hampshire ocean engineering program and a B.S. in mechanical engineering from Cornell University. Endnote: 1. For more information on geo-referenced, digital images of NOAA navigational charts, visit www.charts.noaa.gov/. of imagery. The images, when compared to the chart, often show changes to coastline or coastal construction, such as piers. In some cases, a shoal reported will cor- relate clearly with a shoreline change, corroborating the report. • Crowdsourced bathymetry. There are thousands of boats on the water with GPS units, echo sounders, and logging systems, such as voyage data recorders, chart Chincoteague Inlet, Virginia. The satellite photo shows dramatic changes in the coastline since the last chart update.

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