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.
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.
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.
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)
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.
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.
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.
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.
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.
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.
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.
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.
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.
The NOAA NOAA ENC® contains most of the features currently shown on the corresponding paper chart. The detailed road networks and depictions of buildings in urban areas has been replaced with an "urban area" that is displayed as a tinted area with the associated place name.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.