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Click on a question listed below to jump to the answer on this page.

• What is an Electronic Navigational Chart?
• What are ECS and ECDIS?
• When will NOAA ENC® be available to the public?
• What data coverage will be available?
• How will the public be able to obtain NOAA ENC®s?
• How much does an NOAA ENC® cost?
• Is an NOAA ENC® a simply a copy of the paper chart?
• What are the sources used in compiling NOAA ENC®s?
• Does the NOAA ENC® have all of the features from the chart?
• What NOAA ENC® data is currently available?
• How current is the NOAA ENC®?
• Is NOAA ENC® data copyrighted by NOAA?
• Do NOAA ENC®s enhance marine navigation and will they replace the paper chart completely?
• How often will new editions of NOAA ENC®s be released?
• What is meant by an NOAA ENC® "cell"?
• On what media will NOAA ENC®s be available?
• What hardware and software is required operate NOAA ENC®s?
• Can commercial systems operate and view NOAA ENC® data?
• Will NOAA provide any viewing or navigation software?
• What commercially available software can be used to view NOAA ENC®s?
• What are the uses of NOAA ENC®s?
• What are the benefits of using NOAA ENC®s?
• What capabilities does NOAA ENC® provide that are not available in a paper or raster chart?
• How is the data displayed?
• Does the data look like a paper chart?
• Will NOAA ENC®s be updated via the US Coast Guard Local Notice to Mariners?
• Can a user get a screen print of any displays?
• Can a display be used without GPS input?
• On a ship that transits from one NOAA ENC® to another NOAA ENC®, can both areas be simultaneously shown in a single display?
• Can other ships navigating in the ships area also appear in the NOAA ENC® display?
• How will NOAA ENC®s be updated and maintained?
• What does the date entry mean on the NOAA ENC® download page?
• Do NOAA ENC®s have edition numbers or print dates like paper charts?
• What does the file name of the NOAA ENC® mean?
• What is the CATALOG.031 file?
• What are the other files included with the NOAA ENC®?
• Is the NOAA ENC® a Windows only product?
• What is the difference between the NOAA ENC® and the National Imagery and Mapping Agency Digital Nautical Chart (NIMA DNC™)?

Question - What is an Electronic Navigational Chart?

Answer - It is a vector- based digital file containing marine features suitable for marine navigation. It is based on the International Hydrographic Organization (IHO) S- 57 standard. The NOAA ENC® is intended for use in electronic charting systems (ECS) as well as Electronic Chart Display and Information Systems (ECDIS). NOAA ENC®s can also be used in geographic information systems (GIS) as base map data.

Question - What are ECS and ECDIS?

Answer - Electronic chart systems encompasses any electronic system that uses digital chart data. The chart data can be vector or raster and no specific format is currently defined, although many ECS can use NOAA ENC® data. There are standards being developed for ECS by the Radio Technical Commission for Maritime Services (RTCM www.rtcm.org). Electronic Chart Display and Information Systems (ECDIS) are systems that are certified to meet a suite of international standards: IHO (www.iho.shom.fr) Transfer Standard for Digital Hydrographic Data S- 57, IHO Specifications for Chart Content and Display aspects of ECDIS S- 52, IMO (www.imo.org) Resolution A.817 (19) Performance Standards for ECDIS, and IEC (www.iec.ch) 61174: ECDIS - Operational and performance requirements, methods of testing and required test results. An ECDIS must use "official" NOAA ENC® data to meet all of these standards and may use "official" raster data where NOAA ENC® data is not yet available.

Question - When will NOAA ENC® be available to the public?

Answer - Creation of the database for producing NOAA ENC®s takes time and resources. We currently project that the initial coverage of major commercial ports will be completed by 2002. It is anticipated, however, that NOAA ENC® data will be made publicly available before the entire coverage is complete. We plan to have data available starting in 2001 with updating soon to follow.

Question - What data coverage will be available?

Answer - The nation's 40 major commercial port areas will be completed by the year 2002. This coverage is equivalent to approximately 200 paper nautical charts. NOAA estimates that an additional 400 charts will have to be converted to NOAA ENC® form for complete coverage of U.S. waters.

Question - How will the public be able to obtain NOAA ENC®s?

Answer - NOAA ENC®s will be available for download from the Coast Survey Website (nauticalcharts.noaa.gov).

Question - How much does an NOAA ENC® cost?

Answer - NOAA ENC®s downloaded directly from the Coast Survey Website will be available free of charge. Private companies may offer NOAA ENC®s as part of a service, in which case there may be an associated charge.

Question - Is an NOAA ENC® a simply a copy of the paper chart?

Answer - The NOAA NOAA ENC® program is building the NOAA ENC® production database from a combination of charted information as well as original "source" information. NOAA has compiled critical features such as channel limits, aids to navigation and obstructions from the original documents that were used to put the feature on the paper chart. This means that a feature such as a federally maintained channel was digitized from a 1:2,400 scale drawing as opposed to a 1:20,000 scale chart. The objective is to use more accurate information for features that are critical to the safety of navigation.

Question - What are the sources used in compiling NOAA ENC®s?

Answer - NOAA uses a number of sources in compiling NOAA ENC®s. These include: U.S. Army Corps of Engineers surveys, drawings and permits, U.S. Coast Guard Local Notices to Mariners, National Imagery and Mapping Agency Notices to Mariners, NOAA hydrographic surveys, the largest scale paper chart of the area, as well as other source material that comes in to NOAA from a variety of public and private sources.

Question - Does the NOAA ENC® have all of the features from the chart?

Answer - The NOAA NOAA ENC® will contain most of the features currently shown on the corresponding paper chart. The detailed road networks and depictions of buildings in urban areas will be replaced with an "urban area" that is displayed as a tinted area with the associated place name. Some of the earlier NOAA ENC®s that NOAA produced have limited content and are intended for deep draft navigation only as they do not have many of the alongshore features found on a paper chart. These NOAA ENC®s are referred to as "Version 1" please click on this link for a more detailed description of Version 1 NOAA ENC®s. The Version 1 NOAA ENC®s are being upgraded so that the entire NOAA NOAA ENC® suite will contain all of the features available on the paper chart.

Question - What NOAA ENC® data is currently available?

Answer - Approximately 100 NOAA ENC®s are available for evaluation, familiarization, testing and software development from the Coast Survey Website (nauticalcharts.noaa.gov).

Question - How current is the NOAA ENC®?

Answer - All NOAA ENC®s that are considered "completed" are up to date for the current Notices to Mariners. They will also have any new chart information included within a few weeks of the information's arrival at NOAA.

Question - Is NOAA ENC® data copyrighted by NOAA?

Answer - No.

Question - Do NOAA ENC®s enhance marine navigation and will they replace the paper chart completely?

Answer - NOAA ENC®s and RNCs will eventually replace paper charts for vessels using electronic navigation. NOAA will continue to produce paper charts for those users who do not choose to use electronic navigation. NOAA ENC®s and ECS are the greatest advancement in maritime safety since the introduction of radar to ships.

Question - How often will new editions of NOAA ENC®s be released?

Answer - This is yet to be determined. In paper chart production, new editions are driven by the amount of new information to be applied to the chart as well as how many copies are in stock for use. Neither of these considerations really apply to the NOAA ENC®, so new NOAA ENC® editions may be synchronized to the paper chart cycle or may be on a set schedule, e.g., annually released.

Question - What is meant by an NOAA ENC® "cell"?

Answer - The area covered by an NOAA ENC® is referred to as a "cell." At present, each NOAA ENC® corresponds to the largest scale paper chart in a given area. As the NOAA ENC® begins to contain more detail and the file sizes get larger, it may become necessary to split the cells into smaller areas.

Question - On what media will NOAA ENC®s be available?

Answer - Coast Survey will not provide NOAA ENC®s on any hard media, they will be only available from the Government at the Coast Survey Website (nauticalcharts.noaa.gov). However, private companies may make NOAA NOAA ENC®s available on products that are available on hard media.

Question - What hardware and software is required operate NOAA ENC®s?

Answer - Display of and NOAA ENC® is dependent on navigation software such as an ECDIS. However, the NOAA ENC® is not dependent on unique operating systems or navigation software. Since it is provided in an international, publicly available standard format, any software company that wants to support NOAA ENC® data can implement that capability without restricting the software to a proprietary format or provider.

Question - Can commercial systems operate and view NOAA ENC® data?

Answer - Yes. A number of commercially available systems use NOAA ENC® data. These include both "type- approved" ECDIS software as well as ECS packages.

Question - Will NOAA provide any viewing or navigation software?

Answer - No. NOAA is providing the NOAA ENC® data. It is up to the commercial market to provide software to use it.

Question - What commercially available software can be used to view NOAA ENC®s?

Answer - Please look at the list of software provided on the NOAA ENC® Homepage.

Question - What are the uses of NOAA ENC®s?

Answer - Marine navigation, route planning, and GIS applications are just some the uses for the data as a background display. USCG already uses NOAA ENC® in several Vessel Traffic Systems (VTS) to monitor ship movements in rivers, harbor, and bays in the U.S. Since NOAA ENC® is a vector product, categories of data may be individually selected or queried. Because of this data flexibility, NOAA ENC® is a powerful database supporting various marine and GIS applications.

Question - What are the benefits of using NOAA ENC®s?

Answer - Incorporating digital chart data with a continuous GPS signal for automated vessel positioning enhances safety of navigation. Users can selectively display only the information desired while the computer can continue to process all the information for safety of navigation. Many marine mishaps are due to human error. Vector chart data with proper software applications will enhance safe navigation and provide the mariner with advance electronic warnings of unforeseen dangers.

Question - What capabilities does NOAA ENC® provide that are not available in a paper or raster chart?

Answer - Data can be queried (i.e., vector data is smart data) in a variety of ways, which gives the user much more information than a static paper chart can. The navigator can control the display of the NOAA ENC® data, which allows for a customized display that only shows information critical to safe navigation. The navigation system software can continuously monitor the ship's position relative to all of the features contained in the NOAA ENC®, whether displayed or not, and sound alarms if it detects a hazardous situation. Similarly, the software can check that planned routes will provide safe passage for the vessel by checking for proximity to dangers and crossing areas with insufficient depth.

Question - How is the data displayed?

Answer - This depends entirely on the navigation software or GIS that is being used. An ECDIS will use the symbols and colors required by regulation, but other systems can use whatever symbols the manufacturer chooses.

Question - Does the data look like a paper chart?

Answer - It can, depending on what colors and symbols the display software is using.

Question - Will NOAA ENC®s be updated via the US Coast Guard Local Notice to Mariners?

Answer - Yes. NOAA plans to provide updates for the NOAA ENC® similar to the updates currently provided for the raster chart. These will include all Local Notices to Mariners corrections.

Question - Can a user get a screen print of any displays?

Answer - Depends on the software being used. Most PC platforms support screen prints.

Question - Can a display be used without GPS input?

Answer - Yes, but the ideal navigational situation is to have an automated positioning signal feed into the system displaying NOAA ENC® data for continuous vessel tracking.

Question - On a ship that transits from one NOAA ENC® to another NOAA ENC®, can both areas be simultaneously shown in a single display?

Answer - It all depends on the customer's system capability; nothing in the database precludes this capability.

Question - Can other ships navigating in the ships area also appear in the NOAA ENC® display?

Answer - This depends on the customer electronic navigation systems - nothing in the data precludes display of the data from ship's radar screen or, when adopted, Automated Information System symbology.

Question - How will NOAA ENC®s be updated and maintained?

Answer - NOAA ENC®s will be updated with new source material and Notices to Mariners (both Local and NIMA). The NOAA ENC® production system will be able to convert any new source materials such as hydrographic surveys, Notices to Mariners, etc. for inclusion in the NOAA ENC® database.

Question - What does the date entry mean on the NOAA ENC® download page?

Answer - The date shown on the NOAA ENC® download page is the date that the compressed NOAA ENC® archive was last modified. This usually means that a new, updated cell replaced the NOAA ENC® cell file. It may also mean that one or more of the supporting text or picture files was modified. Users should always make sure that they are using the latest version of the NOAA ENC® and its supporting files.

Question - Do NOAA ENC®s have edition numbers or print dates like paper charts?

Answer - In short, yes they do. Every NOAA ENC® starts with a file header that has various information, metadata, about that particular NOAA ENC®. The header has a number of "subfields," each of which has information about a particular aspect of the NOAA ENC®. One subfield is the edition number, which is a sequential number that works just like the edition number on a paper chart. The first time an NOAA ENC® is issued, it is edition one (1), which is subsequently superseded by edition two (2) and so forth. There is also a subfield called issue date which is the first date that the NOAA ENC® may be used for navigation. Finally, the update application date subfield indicates the last date through which all updates (Notices to Mariners in particular) have been applied.

Question - What does the file name of the NOAA ENC® mean?

Answer - The NOAA ENC® file name format is specified in the IHO S-57 standard. The first two characters, US, indicate that the U.S. Office of Coast Survey, NOAA, produced the NOAA ENC®. The third character indicates the "navigational purpose" of the NOAA ENC® as defined in S-57, a rough indicator of the scale of the NOAA ENC®: 1-overview; 2-general; 3-coastal; 4-approach; 5-harbor; 6-berthing. The remaining characters left of the dot are defined by Coast Survey. The fourth and fifth characters are the two letter postal code for the state where the NOAA ENC® is located (e.g., TX for Texas, NY for New York, etc.) The next two characters are the NOAA ENC®s number and the final character is "M" indicated that the NOAA ENC® is in metric units. The file extension, ".000," for a base NOAA ENC® cell is used for updating. The first update for a cell will be ".001" the next ".002" and so forth.

Question - What is the CATALOG.031 file?

Answer - The CATALOG.031 file is a listing of the cells and ancillary files that are included in an NOAA ENC® "exchange set." Each file has an entry in the CATALOG file so that your software can check to see if all of the relevant files are included. The ".031" extension indicates the edition of S-57 that was used to produce the files.

Question - What are the other files included with the NOAA ENC®?

Answer - Besides the CATALOG file explained above, there is a README.TXT file included that lists all of the NOAA ENC®s with their corresponding paper/raster chart number, title and other information. Each NOAA ENC® may have ancillary files associated with it. These may be text files that are analogous to chart notes on the paper chart or possibly information from the Coast Pilot. There also may be picture files such as .tif or .jpg files that include a picture that is linked to a feature(s) on the NOAA ENC®, such as a picture of a bridge.

Question - Is the NOAA ENC® a Windows only product?

Answer - In short, no. The NOAA ENC® uses the international standard format for vector electronic charts, the International Hydrographic Organization "Transfer Standard for Digital Hydrographic Data, Special Publication S-57." The file format used by the S-57 standard is ISO/IEC 8211, "Information processing - Specification for a data descriptive file for information interchange." This format is designed to be platform and operating system independent and the data files can be used with operating systems such as Windows, Macintosh, UNIX and Linux. However, since the NOAA ENC® is a file of data, a computer needs an application program that is capable of reading the ENC implementation of the 8211 files structure. At this time, the only free viewers that have been made available by software manufacturers are Windows based.

Question - What is the difference between the NOAA ENC® and the National Imagery and Mapping Agency Digital Nautical Chart (NIMA DNC™)?

Answer - The NOAA ENC® is based on the International Hydrographic Organization Transfer Standard for Digital Hydrographic Data, Publication S-57 and is approved by the International Maritime Organization for SOLAS class vessels to use for navigation in an Electronic Chart Display and Information System. The DNC™ uses the Vector Product Format, which is a NATO standard for digital military map and chart data. They are both vector format charts and are based on NOAA nautical charts, just in different formats. The NOAA ENC®, however, has certain critical features such as aids to navigation and channel limits created from larger scale, more accurate information than can be obtained by digitizing a paper or raster nautical chart.

QUESTION: Why is RCDS being proposed as a SOLAS-compliant navigation system?

ANSWER: There are a substantial number of raster-based, electronic navigation systems being sold and used. This experience is showing raster systems to be excellent navigation tools which provide a functionality at least equivalent to the paper chart. Most have features such as real time positioning which are far beyond paper charts. They are also inexpensive and easy to use and update.

It is an IMO responsibility to advance technologies which improve the safety and efficiency of marine navigation. An RCDS Performance Standard will insure that suitable equipment and official data are developed and used. An accepted RCDS Standard will also provide an endorsement of this technology which should encourage its spread. The IMO is thus providing an additional tool for the mariner.

QUESTION: How do paper charts, RCDS and ECDIS compare as navigation tools?

ANSWER: The paper nautical chart is the fundamental tool of marine navigation. It has served for hundreds of years to convey information about the marine environment and for voyage planning and monitoring. The navigation features of the paper chart are well documented in IHO Publication MP-004, Chart Specifications of the IHO .

Raster chart display systems exactly reproduce the familiar paper chart. All chart information is available to mariners in a picture they are experienced at using. RCDS adds real time positioning, electronic tools for voyage planning and monitoring (way points, off-track alarms,...), improved nighttime visibility, access to chart notes, etc. In addition, RCDS provides for the automatic application of official updates issued by national hydrographic offices.

ECDIS does not display an existing chart but constructs a chart-like display which meets the standards adopted by the IMO. It provides all of the navigation functionality of RCDS and adds the capability of additional alarms triggered by the chart data (prohibited area, safety contour,...) and the ability to remove some chart information to simplify the display.

Both RCDS and ECDIS have the disadvantages of higher cost since they require a computer, limited display area, and some small chance of electronic failure. The risk of electronic failure should be no worse than for already accepted devices such as LORAN, GPS, radio, and radar.

QUESTION: What would be the benefits of adopting an RCDS Performance Standard?

ANSWER: Mariners would benefit by having an additional navigation tool with features such as real time positioning. A Performance Standard would help them select a capable system and remain SOLAS-compliant. As ECDIS becomes available, it would find a pool of experienced electronic navigators who would be ready to move up to the more sophisticated ECDIS.

Hydrographic offices would increase their level of mission accomplishment by providing additional data to mariners. For HO's where ECDIS data will not be immediately available or is too expensive to collect and maintain, RCDS can provide an interim solution.

For system manufacturers, it would expand the size of the market and encourage more companies to produce electronic navigation systems. This can only help make ECDIS systems less expensive. In addition, an IMO-approved RCDS could be used as an ECDIS backup.

QUESTION: Why should we move quickly to adopt an RCDS Standard?

ANSWER: RCDS systems are being sold in increasing numbers. IMO should move quickly in order to help emerging systems meet a minimum standard as a means of guaranteeing safety. Also, nations producing official raster chart data need an RCDS Standard. IMO action at this time would prevent the spread of many different national standards.

QUESTION: How can IMO quickly approve an RCDS Standard when the ECDIS Standard took 8 years to write and approve?

ANSWER: First, many of the decisions made for ECDIS apply directly to RCDS. For example, the necessary functions of electronic navigation systems (route planning and monitoring, updating, voyage recording...) are now accepted. This question does not need to be reexamined because the same functions would be required of an RCDS.

Second, much of the time-consuming work that was done for ECDIS does not apply to RCDS. For example, the development of the S-57 feature/object catalog will not be repeated for RCDS because raster charts are exact digital copies of official hydrographic office charts.

Third, there is substantial experience with raster chart systems that did not exist for vector systems when ECDIS was being specified. This practical experience removes much of the uncertainty that was dealt with by time-consuming discussions, simulations and tests of the ECDIS Performance Standard.

QUESTION: Do we really know enough to approve an RCDS Standard?

ANSWER: Yes. The hydrographic offices proposing an RCDS Performance Standard have both practical and analytical data to support RCDS as a suitable navigation tool. It is estimated that in the U.S. alone, over 6,000 raster-based navigation systems are in use. Such experience helps validate the proposed RCDS Standard and the suitability of RCDS as a paper chart replacement.

QUESTION: How does the proposed RCDS Performance Standard differ from the ECDIS Performance Standard?

ANSWER: The proposed RCDS Performance Standard is identical to the ECDIS Performance Standard except where the difference between raster data and vector data requires a change.

RCDS would not have the automated alarms triggered by chart data that ECDIS provides nor could one reduce clutter by turning off chart objects. However, mariners would still have real time positioning, automatic updating and any alarms entered manually (off-track alarm, obstructions...). In addition, the familiar chart image would minimize training time and would allow mariners to use their existing navigation skills immediately.

QUESTION: What might be controversial about the proposed RCDS Standard?

ANSWER: RCDS offers somewhat less capability than ECDIS (e.g. no automated alarms, no turning features off). However, it does offer much more than the paper chart.

Mariners would still benefit by using it when the full functionality of ECDIS was not needed or where a full suite of ECDIS data was not available.

QUESTION: Would the need for raster data put an extra burden on hydrographic offices and slow their efforts to provide ECDIS data?

ANSWER: This decision should be based on the contribution to navigation safety and efficiency not on the convenience of hydrographic offices. However, four nations produce raster charts of their waters (U.S., U.K., Canada, and Australia). All four report that the production of RNC's had no impact on their NOAA ENC® data collection for ECDIS.

The production of raster data is simple, quick and inexpensive. Raster charts cost between $500 (US) and $1,500 (US) each for their initial production depending on the method used. In the U.S., NOAA has achieved savings of $1M annually in its paper chart production and gets raster charts for free by combining the production of the two products. This technology can be made available to other hydrographic offices.

QUESTION: Will approving an RCDS Standard lessen our commitment to ECDIS?

ANSWER: No. It will increase our commitment to the mariner by providing an additional tool that can be used when the full functionality of ECDIS is not needed or where ECDIS data is not available. Its suitability as an ECDIS backup will remove one more barrier to the eventual use of ECDIS.

QUESTION: If RCDS is accepted and used, would mariners switch to the more powerful ECDIS as it becomes available?

ANSWER: A system which meets the proposed RCDS Performance Standard should become ECDIS-compliant merely by upgrading the software. The expense and inconvenience is thus minimal. Manufacturers in the USA are already demonstrating navigation systems that can use several types of raster data, including RNC's and several types of vector data, including NOAA ENC®'s.

QUESTION: How does RCDS deal with charts of different map projections and on different datums?

ANSWER: Metadata included with the RNC's identifies the projection and datum for each chart. The navigation software then converts positioning system information into the chart's projection and datum in real-time. If a chart's datum is unknown, the RNC metadata includes the parameters necessary to map geographic positions to RNC pixel locations calculated from the grid intersections printed on the chart.

QUESTION: How can raster charts replace paper charts when only a portion of a chart can be seen at any one time?

ANSWER: RCDS offers exactly the same field of view capability as ECDIS which has already been accepted by the IMO/IHO. Both RCDS and ECDIS specify a 270mm x 270mm screen size. Whether displaying a 1:40,000 scale RNC or 1:40,000 scale NOAA ENC® data, the width of the computer screen will only show approximately 5.8 nm.

RCDS and ECDIS deal with a computer's limited field of view in a similar way. RCDS users load the next smaller scale chart. ECDIS users zoom out and let the software suppress information and resize the remaining text and symbols -- in essence creating a smaller scale chart dynamically. Also, the ability to pan across a chart or to open multiple charts of different scales at the same time gives RCDS and ECDIS increased viewing capability.

QUESTION: ECDIS took 10 years to specify and accept. Is the IMO being too hasty in trying to accept RCDS in substantially less time. Has it been adequately studied?

ANSWER: The ground breaking efforts that led to adoption of ECDIS have paved the way for more rapid adoption of RCDS. Advances in computer technology and new navigation software permits a performance standard for RCDS that is nearly identical to that of ECDIS. In fact, the Technical Work Group of NAV 43 developed a standard for RCDS which provides ECDIS with the capability of using official raster nautical charts. This is the so-called "dual-fuel" concept. Mariners have considerably more experience with raster-based charting systems than with ECDIS because raster nautical charts have been available worldwide for some time. This experience helps us know that RCDS is safe and enhances navigation safety and efficiency. Surveys by the UK and the USA testify to the functionality and safety of RCDS as a stand-alone tool for navigation planning and route monitoring. Results from at-sea trials conducted by The Netherlands, Ireland, and a joint program testing the dual-fuel concept soon will be published.

QUESTION: How can one plot a course and navigate that course when it crosses several charts which may be of different projection, scale and datum?

ANSWER: Advanced RCDS software automatically switches charts when the vessel arrives at the edge of the present chart. The new chart is displayed in a scale as close to the previous chart as possible. The datum issue is addressed above. Projection differences are automatically accommodated by advanced RCDS software.

QUESTION: Does chart clutter make a RCDS unusable?

ANSWER: RNC's are exact copies of paper charts and contain all the detail of those original charts. Hydrographic offices had worried that this would appear "cluttered" when displayed on a computer monitor. However, users are reporting that "chart clutter" is not a serious problem with raster charts.

QUESTION: Is vector NOAA ENC® data inherently better than raster RNC data?

ANSWER: They both have strengths and weaknesses. Vector data allow displays to be decluttered and support automated alarms based on the data itself. Raster data provides most of the ECDIS functionality but are far easier to produce and are more widely available. However, this is a misleading question. The real questions are: Does RCDS provide the tools for a mariner to safely navigate? (Yes, tests at sea so indicate.) Does it enhance safety of over the paper chart? (Yes, a survey of U.S. mariners overwhelming attests)

QUESTION: How are chart notes and legends found on a raster chart?

ANSWER: Hydrographic offices provide the coordinates of a rectangle surrounding each note, legend, tide box or channel depth table. They also provide reference point coordinates for each note. RCDS software places an unobtrusive (or invisible!) icon at the reference point. When the icon is "picked" by the mariner, a second small window on the chart opens, displaying the note. This method would allow notes to be displayed automatically as a mariner's ship approaches the coordinates of the reference points.

QUESTION: Can text and symbols be resized (rescaled) when one zooms in and out on a raster chart?

ANSWER: No. Text and symbols will be enlarged or reduced as one zooms in and out. If this results in text that is too small or too large to read, it means that you are operating out-of-scale and should switch to a different scale chart.

QUESTION: Can the mariner limit the information that is displayed on the RCDS?

ANSWER: No. RCDS displays a complete RNC which is a copy of a paper chart. The concern that displaying all chart information may be too cluttered is proving not to be the case. A benefit of this characteristic is that critical information is never accidentally turned off.

QUESTION: Can data be interrogated with RCDS as it can with ECDIS?

ANSWER: No. RCDS cannot directly interrogate an RNC which is merely an electronic picture of a paper chart. However, since the RNC displays all of the paper chart, most information is already displayed and the RNC does not need to be interrogated.

Additional data which may accompany an RNC, such as operator-entered items or other data bases can be interrogated in real-time and used to trigger alarms or perform other operations. For example, a mariner may designate hazards on or near his route. RCDS would then trigger alarms when these hazards were approached, even if the relevant chart was not being displayed at the time.

QUESTION: What kind of automatic alarms and indicators does an RCDS support?

ANSWER: RCDS issues automatic indicators when an RNC is being displayed over scale, when a larger scale chart is available and when the chart is on a different reference system from the positioning system. RCDS issues automatic alarms for exceeding an off-track limit, deviating from a route, approaching a critical point, using a chart on a different geodetic datum, approaching a critical point/line/area and for an RCDS malfunction.

RCDS allows mariners to enter points, lines and areas to designate other alarm items. A mariner may enter obstructions, navigable limits (rough safety contours), prohibited areas, etc. anywhere on a chart or on any chart. These are monitored by RCDS software and alarms can be triggered even though a particular chart is not being displayed at the time an alarm feature is approached.

QUESTION: Is it possible to integrate a radar presentation with the RCDS display?

ANSWER: Yes. Navigation software now filter the radar picture so that it and the raster display are legible.

QUESTION: Can RNC's have daytime and nighttime colors like NOAA ENC®'s?

ANSWER: Software can remap the RNC's colors and their brightness to any other colors and brightness available on the host computer. Thus dusk, twilight and nighttime colors can be specified. National hydrographic offices providing RNC's should specify a pallet for their charts which is most suitable for those different conditions.

QUESTION: Won't acceptance of RCDS slow our progress towards ECDIS?

ANSWER: No. Instead, it will increase our commitment to the mariner by providing an additional tool that can be used when the full functionality of ECDIS is not needed or where ECDIS data is not available. Also, its suitability as a backup for ECDIS will remove one more barrier to the eventual use of ECDIS. As ECDIS data sets become available, professional mariners and others who would benefit from the increased functionality of vector data will adopt that technology.

QUESTION: Has there been sufficient experience at sea with RCDS to allow it to be used in place of the paper chart?

ANSWER: Given the worldwide availability of raster nautical charts and the proliferation of electronic display systems capable of using raster chart data -- including "dual-fuel" capable ECDIS - there is undoubtedly more experience at sea navigating with raster charts than with ECDIS data.

QUESTION: Why are some people and some countries opposed to RCDS?

ANSWER: They oppose RCDS for a variety of reasons, including a vested interest in ECDIS, fear that official RNCs will compete with privately produced data, and concern that RCDS will delay and/or compete with ECDIS. None of these reasons are connected with the efficacy of RCDS as an instrument for safe navigation, which should be the only concern in this matter.

QUESTION: How does RCDS provide an adequate look-ahead capability when you can only see a small part of a chart on the computer screen?

ANSWER: Consider the following 3 points.

Point 1

An RCDS offers exactly the same look-ahead functionality provided by an ECDIS which has already been accepted by IMO. Both RCDS and ECDIS specify a 270x270 mm screen size. Whether displaying a 1:40,000 scale RNC or 1:40,000 NOAA ENC® data, the width of the computer screen will only show about 5.8nm.

Point 2

RCDS and ECDIS deal with a computer’s limited field-of-view for look-ahead capability in a similar way. RCDS users load the next smaller scale chart. ECDIS users zoom out, and let the software suppress information and resize the remaining text and symbols -- in essence creating a smaller scale chart dynamically. Also, the ability to pan along one’s track or to open multiple charts of different scales at the same time gives an RCDS (and ECIDS) increased look-ahead functionality.

Point 3

A paper chart only offers the preferred look-ahead capability if one’s location is near the edge. A 1:40,000 scale chart on A0 size paper with a border around the neatline only depicts a 17nm x 25 nm area. Charts on paper of A1 size or smaller would have proportionately less look-ahead distance.

Finally, RCDS and ECDIS both offer automatic look-ahead. RCDS looks ahead and triggers alarms using mariner-entered data. ECDIS looks ahead and triggers alarms using the NOAA ENC® data. Both RCDS and ECDIS offer an improvement in look-ahead capability for mariners over today’s paper chart.

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