NOAA Raster Navigational Charts (RNC)

NOAA, National Ocean Service, Office of Coast Survey, Marine Chart Division is responsible to build and maintain a suite of more than 1000 nautical charts that are used by commercial and recreational mariners to navigate the United States and U. S. territory waters safely.A Nautical Chart is a graphic portrayal of the marine environment. They are used to lay out courses and navigate ships by the shortest and most economically safe route. They can also serve as base maps for resource management and shoreline development planning by state and local government.Charts depict the location of the shoreline, minimum water depths, aids to navigation, hazards to navigation, the nature and form of the coast, water depths, the general character and configuration of the sea bottom, the rise and fall of the tides, protected areas, and the characteristics of the Earth's magnetism.The suite of charts is compiled and maintained with data provided by federal, state, and private partners such as the National Ocean Service elements, United States Coast Guard, United States Army Corps of Engineers, United States Power Squadron Auxiliary, Port Authorities.The charts are currently available as Lithographically printed paper charts, Electronic Raster Nautical Charts (RNCs), up-to-date paper charts (printed with print on demand technology), and are now offered as Digital Vector Electronic Nautical Charts (ENC).The NOAA RNCs are electronic images of the NOAA paper charts. The NOAA RNCs were productized with a successful Cooperative Research and Development Agreement (CRADA) with private sector partner BSB Electronic Charts, a subsidiary of Maptech, Inc. Andover, Massachusetts. As of November 1, 2005 the NOAA RNC's are available for free download via the NOAA website.

These product offerings are an integral part of NOAA's long term strategy for producing paper and electronic charts for navigation of U.S. waters. Charts are carriage requirements for commercial vessels.

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The official NOAA raster charts are updated weekly by NOAA for critical Notice to Mariners corrections and are composed into the established BSB format and distributed by the NOAA CRADA partner without cost to the government. In the year 2000, NOAA introduced a service that updates the suite of RNCs weekly for critical Notice to Mariners corrections. This service distributes electronic "patches" by email to subscribers of the service on a weekly basis. The "patches" are then automatically applied to the raster charts, thus updating them for critical chart changes published in the Notice to Mariners. This service is unique in the world. With the availability of this service, the raster nautical charts are suitable for use by professional mariners and will meet international standards for electronic charts.Each chart is published periodically as a new edition depending on several parameters such as critical corrections, changing physical conditions, up to date data availability, high vessel traffic area, and demand. Included here are the key definitions used in the update record.Last Update Type - The type of chart updates contained in the update file. "NCE" indicates a new chart edition corresponding to the release of a new NOAA paper chart. "NTM" indicates that the Chart Update contains Notice toMariner corrections.Revision Number - The Chart Update number. For example, an NTM chart, 34.8 means that this is the 8th Chart Update to NOAA chart edition 34.00. For an NCE chart, 35.00 means that this is the 35th new chart edition update, which is to be applied to NOAA chart edition 34.00.Last Updated Date - The date of the most recent Notice to Mariners correction made to the chart by a NOAA cartographer. This correction was based on a Notice to Mariners published by the US Coast Guard, NIMA, CHS or chart change issued by NOAA.Cleared Date - The date through which NOAA cartographers have cleared the chart as being up-to-date. If the Cleared Date is more recent than the Last Updated Date, no additional changes are necessary during the period between the two dates.

The Nautical chart features are according to the U. S. Nautical chart symbols, abbreviations and terms which are Chart No. 1. The NOAA charts are built and maintained according to the policies and procedures documented in the two volumes of the Nautical Chart Manual. The Marine Chart Division, Quality Assurance Policy and Standards Branch (QAPSB) manages questions in reference to symbols, abbreviations, policy and procedures.

https://www.nauticalcharts.noaa.gov/publications/us-chart-1.html

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To be used for navigation and/or as per agreement with the NOAA RNC chart distributor and distribution network.

The Nautical chart features are according to the U. S. Nautical chart symbols, abbreviations and terms which are in Chart No. 1. Chart 1 can be found at http://chartmaker.ncd.noaa.gov/mcd/chartno1.htm.The NOAA charts are built and maintained according to the policies and procedures documented in the two volumes of the Nautical Chart Manual. Questions in reference to symbols, abbreviations, policy and procedures are managed by the Marine Chart Division, Quality Assurance Policy and Standards Branch (QAPSB). For inquiries visit: http://ocsdata.ncd.noaa.gov/dr/inquiry.asp

The art and science of navigation, piloting, and chart making has not been immune to the effects of technology.Prior to 1995, The paper charts were composed manually. In 1995 the paper charts were scanned to create the raster charts. Both, the paper and raster charts are composed from the same digital files.The availability of digital chart products and Differential Global Positioning System (DGPS) has drastically changed navigation. Navigation systems using DGPS for locating a vessel's position on the earth have put mariners in a unique predicament due to a false perception of greater positional accuracy of features portrayed on the charts. In many cases, the DGPS is more accurate than the surveying technology that was used to put the soundings and features on the nautical chart, paper or raster. This discrepancy is even more pronounced when chart scale is taken into consideration. On a 1:40,000 scale chart, a feature could have a potential error of 40 to 80 meters (about 130-160 feet) due to scale alone. This is often the cause of the "ship on the pier" situation, where the vessel tied up at the pier appears on the navigation system to be on the pier rather than alongside.Another source of this type of discrepancy is that symbols on a chart of a given scale may be a representation for multiple real features that are too close together to be shown at chart scale. Similarly, symbols may be displaced from their original location for legibility and presentation. This also applies to products derived from paper charts, such as raster charts and vector charts created by digitizing the paper chart The NOAA Nautical Chart Manual has an extensive description of the horizontal datum.

Nautical Charts are navigational tools. Thus, depths are biased for navigation purposes. Charts use multiple vertical datums (Mean higher high water [MHHW]; Mean high water [MHW]; Mean sea level [MSL]; Mean low water [MLW]; Low water datum [LWD]; Mean lower low water [MLLW]; Gulf Coast low water datum [GCLWD].) The NOAA Nautical chart manual has an extensive description of the vertical datum used. Sounding datums used in coastal areas for nautical charting are determined by local observations, ideally over a period of 19 years. The official time period over which tide observations are taken to obtain mean values for tidal datums has been standardized by NOS. The present National Tidal Datum Epoch is from 1983 through 2001. There have been three epochs used previously over the past century: 1924 through 1942, 1941 through 1959, and 1960 through 1978. The individual chart title block documents the datum used for that chart.

The charts are navigational tools. Sounding datums used in coastal areas for nautical charting are not referred to the 1929 datum but are determined by local observations, ideally over a period of 19 years. The official time period over which tide observations are taken to obtain mean values for tidal datums has been standardized by NOS. The present National Tidal Datum Epoch is from 1983 through 2001. There have been three epochs used previously in the past century: 1924 through 1942, 1941 through 1959, and 1960 through 1978. The individual chart title block documents the datum used for that chart. Charts use multiple vertical datums (Mean higher high water (MHHW); Mean high water (MHW) ; Mean sea level (MSL); Mean low water (MLW); Low water datum (LWD); Mean lower low water (MLLW); Gulf Coast low water datum (GCLWD). Each organization that provides source data to be applied to the chart has data acquisition and data processing and survey parameters such as vertical and horizontal datums, and quality assurance standards. The Marine Chart Division uses source data according to the policy and procedures specified in the charting manual for each source provider. The density of charting features depends on the scale of the chart or chart inset.

It is imperative to recognize that when a symbol, abbreviation, or policy changes, it does not require that all preexisting data on the charts change. Therefore, there are inconsistencies on the charts depending on policy at the time the feature was applied or updated.