Farewell to Traditional Nautical Charts

Sunsetting NOAA raster nautical charts has started. What does that mean?

Sunsetting is a term that refers to purposely and systematically phasing out a product or service.

In 2019, NOAA announced its Sunsetting of Raster Nautical Charts in the Federal Register. The raster sunset program will gradually end production and maintenance of NOAA traditional paper and raster nautical chart products. Beginning in 2021, NOAA will start canceling its traditional nautical charts. The process is expected to be completed by January 2025.

Details about the NOAA Raster Sunsetting are provided through the section tabs below.

NOAA produces nautical charts in two different formats, called raster and vector. Each of these types are compiled and distributed using different methods.

Electronic navigational charts (ENCs)

The ENC product format is specified by the International Hydrographic Organization (IHO). Each ENC is a digital database that stores the location and shape of charted features as pairs of latitude and longitude coordinates. This is known as "vector format" data. Database records associated with each feature provide detailed information, such as the feature's color, shape, height, purpose, quality of position, and other attributes. The data contained within ENCs can be used by electronic navigation systems to enable safer voyage planning and route monitoring. This includes initiating warnings and alarms when a ship is heading into shallow water or toward other dangers to navigation. Updated ENC revision files are available weekly. When ENC revision data is loaded many navigation systems apply these updates automatically. ENCs will continue to be produced and enhanced after all raster format charts are canceled.

Typical small scale portrayal of ENC data covering Entrances to San Francisco Bay.

A new ENC-based option for paper charts

The NOAA Custom Chart (NCC) application was developed to enable users to create their own customized charts directly from the latest NOAA ENC data. While these custom charts do not fulfill U.S. Coast Guard carriage requirements for regulated commercial vessels, they contain the same up-to-date information contained on ENCs.

Traditional paper and other raster nautical charts

Raster charts include traditional paper nautical charts and the corresponding digital images of these charts. These charts are composed of a grid of columns and rows of color pixels - or dots of ink on paper charts - which form the text, linework, and other symbols that make up the chart. The scale, symbolization, text placement, and orientation of the chart is fixed when the chart is compiled. All types of raster charts will be canceled through the sunset program.

Entrance to San Francisco Bay paper nautical chart.

  • Paper nautical charts - Printed and distributed through NOAA's certified print-on-demand (POD) chart agents. These are the traditional charts that have been published by NOAA and the Coast Survey for over 170 years. Mariners using paper nautical charts must apply U.S. Coast Guard (USCG) Local Notices to Mariners (LNM) and National Geospatial-Intelligence Agency (NGA) Notices to Mariners (NM) corrections by hand to keep their paper charts up to date.
Other NOAA raster products, based on the paper chart images, will also be canceled when the corresponding POD chart is canceled. These are:
  • Raster navigational charts (NOAA RNC®) - Full-size, geo-referenced, digital images of NOAA paper nautical charts. These are sometimes referred to as "BSB format" charts and are compatible with some electronic chart display systems. BSB are the initials of each of three companies that were part of a NOAA cooperative research and development agreement that developed the format.
  • Full-size nautical chart PDF images - Full-size, geo-referenced, digital images of NOAA paper nautical charts in Adobe Portable Document Format (PDF).
  • BookletCharts™ - Reduced-size replicas of POD charts, which have been divided into a dozen or more 8.5"x11" pages.
Three raster data related services will also be shut down as part of the raster sunset program. These services will be sustained as raster charts start to be canceled, but as more charts are removed, the patchwork nature of the available data will eventually limit the utility of the services and they will be taken down.
  • RNC Tile Service - Standardized nautical chart tilesets, derived from BSB format NOAA RNC® data. These are geo-referenced charts compatible with the Web Map Tile Specifications (WMTS) and Tile Map Service Specification (TMS).
  • Seamless Raster Navigational Chart Services - Family of services that incorporate RNCs into a unified, collarless (chart margins removed) mosaic, which displays only those charts appropriate for the viewing scale and map extent requested.
  • RNC Viewer - Online viewer that provides a seamless display of raster chart images.

There is a growing need for ever more detailed nautical charts. This is driven by several factors, including larger ships now entering ports and transiting channels with the tightest of under keel clearances - requiring more precise depth information, the greater adoption of (in some cases, the requirement for) use of digital charts, electronic navigational systems, and GPS - requiring greater positional accuracy. The International Maritime Organization (IMO) and the International Convention for the Safety of Life at Sea (SOLAS) require nearly all commercial ships on international voyages to use ENCs for navigation. The U.S. Coast Guard has allowed commercial ships on domestic voyages within U.S. waters to use ENCs in lieu of paper nautical charts since 2016. At the same time the use of traditional paper nautical charts is decreasing. Sales of NOAA print on demand paper nautical charts have dropped more than 50% since 2010.

Guided by these trends, NOAA initiated a program to sunset its traditional paper nautical charts and the corresponding raster chart products and services. This enables focusing resources on improving the coverage and content of the digital chart format that is used throughout the world for navigation, the electronic navigational chart (ENC). Since 2010, subscriptions for individual NOAA ENC charts provided by Regional ENC Coordinating Centers (RENCs) have quadrupled. (The RENC concept was developed by the IHO to ensure that ENC data complies with international standards and to coordinate the distribution of ENCs from producing nations to data users.)

ENC data is produced by scores of other countries and used by mariners around the world. In addition to the Electronic Chart Display and Information System (ECDIS) equipment that the IMO requires large vessels to use to display ENC data, ENCs can now be used in many electronic chart display, chart plotter, mobile app, and GPS systems used by other professional and recreational mariners. These are clear indications that ENCs are already an important part of marine navigation and that they are the foundation upon which future marine navigation systems and other marine related data are being built.

Chart of U.S. ENC and Paper Nautical Chart Sales 2010-2020.

At the end of 2020, NOAA maintained over 1000 individual paper and raster nautical charts, comprised of over 2000 separate main chart panels and insets, compiled in over a 100 different scales. Producing and distributing raster charts requires separate computer software and data storage, as well as specialized cartographic training and processing that is not needed to make ENCs. NOAA now maintains over 1600 ENCs and is carrying out an ambitious program to replace much of the existing ENC coverage with more detailed (larger scale) data. When completed, the enhanced ENC product suite will consist of over 9000 ENCs in eleven standard scales. NOAA has only been able to create and maintain this enhanced suite of ENC products by redirecting resources previously used to update and distribute traditional paper and raster nautical charts.

Initial set of chart cancellations

Modifications to the USCG local notice to mariners (LNM) and other processes at NOAA were required to implement the new "Last-Edition" status that will provide a six-month notice of a chart’s cancellation. To test the various system modifications, the 1:40,000 scale, Chart 18665 of Lake Tahoe was selected as the first chart to be canceled as part of the raster sunset program. A LNM published in February 2021 announced that edition 11 of chart 18665 would be the last edition published and the chart would be canceled in August 2021.

General order of subsequent chart cancellations

In some regions, chart cancellations will progress from the largest to the smallest scale charts. For example, it is anticipated that in some cases the larger scale harbor charts will be canceled before the sunsetting process moves on to start canceling the next smaller scale approach scale charts. In other regions, these larger scale charts may be canceled later in the process due to commercial or national security reasons.

This mirrors the general strategy being applied to the creation of new, reschemed ENC coverage. The largest scale ENCs are being created along large portions of the coast before the next smaller scale ENCs are created. Cancellations will often follow the creation of new, reschemed ENC coverage. Progress of the ENC rescheming effort may be tracked on the Status of New NOAA ENCs.

Other factors considered for canceling charts

Although it is preferred that new reschemed ENC data is available before the corresponding raster charts are canceled, there may be situations where this is not the case. As described in the "Paper and raster chart content is starting to differ from ENCs" section, below, the only updates NOAA is now applying to raster charts are those critical to navigation. If ENCs and the corresponding raster charts get too far out of sync, the associated charts may be identified for an earlier cancellation. NOAA is also looking at sales and download volumes over the past few years; a chart with low sales or downloads may be canceled earlier in the process.

Six-month Last Edition note and lists of canceled charts

Six months before a chart is canceled, NOAA will update the chart with a note in the lower left corner stating the chart’s status as a "last edition" and the date on which it will be canceled. The note will look like this.

Chart cancellation notice.

NOAA will also update the List of Latest Chart Editions on www.nauticalcharts.noaa.gov to indicate that the last edition of the chart has been published. There are two formats for this information, the PDF Dates of Latest Editions document and the HTML NOAA Chart Dates of Latest Editions webpage.

In the PDF, "(L)" is placed next to the chart number and the date on which it will be canceled will be shown in the "Can Date" column, as shown for chart 16543, below. When the chart is canceled six months later, the chart number will be marked with "(X)" and moved from its position in the list of active charts to a cumulative list of canceled charts (since 2018) that is appended to the end of the list of active charts, as shown for charts 14982 and 14983, below.

Dates of latest chart editions.

In the webpage version, "LAST EDITION" is added before the chart title, and "(Chart will be canceled on MM/DD/YY)" will appear on the next line, as shown for chart 16543, below. When the chart is canceled, the chart number will be moved from its position in the list of active charts to a cumulative list of canceled charts at the bottom of the page, as shown for charts 14982 and 14983, below.

Dates of latest chart editions.

A complete list of just the last-edition charts may been viewed by clicking on the "Pending Chart Cancellations" link at the top of the HTML version of the List of Latest Chart Editions webpage. This list may be sorted either by chart number or by cancellation date.

In addition to the paper Print on Demand version of the chart being canceled, all associated raster products will be removed from the NOAA website. These are:

  • Raster navigational charts (NOAA RNC®)
  • Full-size nautical chart PDFs
  • BookletChart™ PDFs
  • RNC tile service images

Local Notice to Mariners

Concurrently, the U.S. Coast Guard will issue a Local Notice to Mariners to announce that no new editions of the chart will be published and the date it will be canceled. The notice in Section IV of the LNM will look like this.

Local Notice to Mariners example.

Another Local Notice to Mariners will be issued to announce the cancellation six months later. The notice in Section IV of the LNM will look like this.

Local Notice to Mariners example.

The USCG Local Notice to Mariners and Light Lists, and the NOAA U.S. Coast Pilot® make copious references to NOAA chart numbers. These help users find the document sections that cover the areas they are interested in. When a NOAA paper chart is canceled, it no longer meets USCG carriage requirements and the Coast Guard will stop issuing local notice to mariners (LNM) for the chart. References to canceled charts will not appear in LNMs, Light Lists, or the Coast Pilot.

However, changes in the positions and characteristics of buoys, beacons and lights, and other "notice-worthy" items will continue to arise. There will still be a need to know the "general neighborhood" in which various features of interest are situated. The USCG and other federal organizations, including NOAA and the U.S. Army Corps of Engineers are collaborating within the Waterway Harmonization Project to develop a common, standardized set of georeferenced points of interest throughout U.S. navigable waters. From this, a hierarchical set of names are being developed for precisely defined bodies of water. These waterway names will provide a way to "drill down" to identify distinct locations, such as "Atlantic Seacoast > Chesapeake Bay > Potomac River > St Marys River." The names will ultimately replace chart numbers in Local Notice to Mariners, Light Lists, the Coast Pilot, and other documents that currently reference NOAA chart numbers.

Chart Numbers and ENC names

The footprints and scales of NOAA ENCs were originally based on the footprints and scales of the corresponding paper nautical charts. NOAA has developed a new regular, gridded scheme that will replace the legacy ENC cells. Although there was a strong correlation between raster chart and ENC footprints in the past, this relationship will dissolve as the ENC rescheming project proceeds. Thus, ENC names will not be useful to reference the footprints of cancelled charts. The Coast Pilot section headings currently provide references to ENC names, in addition to chart numbers. ENC names will eventually be removed from the Coast Pilot and replaced with names created by Waterway Harmonization project.

Paper and raster chart content is starting to differ from ENCs

Prior to traditional chart production ending, users may notice differences between paper charts and ENCs. There are two broad categories of data that are applied onto NOAA ENCs and paper / raster nautical charts- "Critical Corrections" and "Routine" source. "Critical Corrections" may be newly discovered shoals or other dangers to navigation, as well as changes in the positions or characteristics of aids to navigation (buoys, beacons, and lights). These are typically changes that are published by the U.S. Coast Guard in weekly Local Notice to Mariners. Critical corrections are applied to ENCs first, then applied to paper and raster nautical charts. These changes generally appear on both product types (raster and ENC) within a week of each other.

However, new "Routine" source data are now ONLY applied to NOAA ENCs and not to traditional paper and raster nautical charts. Routine data includes the results of ordinary hydrographic and shoreline surveys, which could be extensive. Any specific dangers revealed during routine surveys are extracted from the data and classified as Critical Corrections to be applied to all products.

Advantages of focusing on ENC production

The legacy of the paper charts from which ENC data were first digitized, starting in the early 1990s, lives on in the current suite of ENCs. The footprints and scales of NOAA ENCs were inherited directly from corresponding paper charts and the resulting ENC product suite now consists of hundreds of irregularly shaped cells compiled in over 100 different scales.

Adjoining paper charts, even with the same navigational purpose (harbor, approach, coastal, etc.) are often compiled at slightly different scales to accommodate different chart orientations, paper sizes, or a desire to extend a chart's coverage to include harbors or other key features at opposite sides of a chart. Different depth contour intervals are often used on different scale charts and the process of "edge matching" adjoining ENC cells built from these different scales can be challenging.

The new NOAA ENC re-scheming program is replacing the current irregular layout of ENCs with a regular grid of rectangular shaped ENCs. This multi-year effort will increase the size of the ENC product suite to about 9,000 ENC cells. Many of these will be compiled at larger scales than the ENCs they replace.

The new ENC scheme reduces the set of compilation scales to 11. This reduction makes reviewing and resolving discontinuities much easier, because new adjoining ENCs with the same navigational purpose are likely to be of the same scale. Reschemed ENCs will correct alignment errors among features on adjoining ENCs and create a standard set of depth contours in integer meter units.

ENCs show controlling depths in federally maintained channels

Federally maintained channels are broken into a series of individually named sections called "reaches." There are two different depths associated with each reach that are reported by the US Army Corps of Engineers (USACE) - project depth and controlling depth. Project depths are the depths to which a channel reach was designed to be dredged when constructed by the USACE. Reaches may or may not be maintained to the project depth by dredging after completion of the channel. In other words, the actual depth of the channel may be shoaler than the project depth, such as Reach B in the figure below. Controlling depths, or minimum depths, are the least depths within the limits of a channel reach. Ships with drafts deeper than a reach’s controlling depth cannot transit through the channel safely. That is, the depth "controls" that size of the ships that can use the channel.

Water depth illustration.

An issue of timing

Controlling depths are collected by the USACE during periodic sonar surveys of federally maintained channels. Typically, the USACE is able to post new controlling depth information on their website before Coast Survey is able to update and publish the changes on paper nautical charts. This inconsistency between the USACE website and NOAA charts - both of which are consulted by mariners and pilots - can to lead to confusion.

To eliminate inconsistencies, NOAA has transitioned its paper nautical charts to show only project depths for each channel reach. Project depths can give mariners a general idea of the depth for which each section of a channel was designed, but not the most recent survey’s controlling depths. ENCs will continue to show controlling depths and mariners transiting federally maintained channels are encouraged to use ENCs for this reason.

Suitable for framing or as a historical reference, previous editions of all NOAA charts - including the "Last-Edition" of each paper nautical chart - may be downloaded for free from the NOAA Historical Map and Chart Collection. Nautical charts, other maps, and documents, such as the Coast Pilot, dating back to the mid-1800s are included in the collection.

Traditional training charts are "frozen in time" and are used by many mariner training and testing institutions. Training chart numbers include a "TR" suffix, such as 1210TR, "Martha’s Vineyard to Block Island" and are marked, "For instructional purposes only. Not to be used for navigation." The Historical Map and Chart site has a direct link to Training Charts and paper copies may also be purchased from many commercial providers for about $10.