Raster Vs Vector Chart

[Josephina]

ManyCanadian Hydrographic Service (CHS) charts are available in digital form as either a Raster Navigational Chart (RNC) or as a vector Electronic Navigational Chart (ENC). Both charts use navigation software to provide navigators with an electronic alternative to paper charts, resulting in safer navigation.

ENCs are "smart charts", which means the user can click on different features, such as a light or buoy, to retrieve additional information not available in paper or raster charts. For example, a wharf appears only as an image on an RNC, but an ENC can identify it as a wharf and attach attributes to it such as height, length, age, ownership, number of berths, etc. This additional data, which is contained directly within the ENC, might otherwise only be available by consulting the relevant Sailing Directions publication.

ENCs used on an Electronic Chart Display and Information System (ECDIS) and integrated with other data such as GPS position, radar, planned routes, heading, speed, and draught, assist mariners and alert them to sailing hazards, warnings, and dangerous situations. ENCs are powerful and flexible navigational tools that provide users with more control over the display of the chart.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

3a8082e126