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Alaska Bathymetry: What are Smooth Sheets?

(Mouse over boxed areas for additional smooth sheet details) Pictured above: Smooth Sheet H05152 showing Kiliuda Bay with significant place names in block letters and important features indicated. See "Smooth sheets: How to work with them in a GIS to derive bathymetry, features and substrates" for complete information.

Physically, a paper smooth sheet with muslin backing was the final product of a hydrographic survey. The soundings were drawn on a smooth sheet, along with the shoreline, geographic features (e.g., kelp beds, rocky reefs, islets, rocks), seafloor substrates (e.g., gravel, sand, mud), and the navigational signals to provide a visual record of the hydrographic survey, which could be annotated as new information became available.

Though more detailed than navigational charts, smooth sheets are not intended for use in navigation. Instead the smooth sheets, many dating back to the 1930s, were used as internal documents by the hydrographic agency. Only after they were scanned, digitized, and posted to NGDC (Wong et al. 2007) did they become widely used by non-hydrographers. The NOS navigational charts (not smooth sheets) are the legal standard for safe navigation on the ocean (Title 33 Code of Federal Regulations 164).

All scientists who conduct research on the ocean have probably used the small-scale navigational charts for a variety of cruise planning and data analysis tasks without knowing that perhaps ten times as much information was available from the precursor hydrographic surveys, represented by the smooth sheets. Others who are aware of the smooth sheet resource might not understand some of the details about successfully using this rich data resource. Therefore, now that electronic copies of the smooth sheets are readily available, it is worthwhile for non-hydrographers to understand how to use them.

Guide for Working With Smooth Sheets:

The guide "Smooth sheets: How to work with them in a GIS to derive bathymetry, features and substrates" is intended to provide the user with enough information to understand and properly utlize the smooth sheets and their associated data. The guide should be cited as: Zimmermann, M. and J. Benson. 2013. Smooth sheets: How to work with them in a GIS to derive bathymetry, features and substrates. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-249, 52p.



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