ECDIS and Mapping System
Datum (mapping system) - a mathematical model of the Earth, on which the sea chart. If mapping system position sensor and mapping system nautical chart different, the system is necessary to make the conversion. If this is not done, it may cause some errors in nautical miles. The difference between the two mapping systems - not a constant, but depends on the position. This means that the difference between the WGS-84 and local mapping system commonly used in paper maps, in general, does not apply to electronic nautical charts.
Historically, mapping systems that are the traditional paper charts national mapping systems. Many paper maps are not marked in any mapping system they are made, so compatibility with electronic maps can be difficult. On some paper charts are printed instead of the mapping system correction conditions for corrections satellite positioning system WGS 84. Correction conditions apply, but only for paper maps that are questionable.
Electronic Marine Maps
To date digital maps based mainly on paper maps - raster or vector format translated, leading to the corresponding transfer local mapping system.
• Cartographic material ARCS (bitmap) for each card includes a polynomial system allows ECS to resolve the difference between mapping system WGS-84 and local mapping system with an accuracy sufficient for the administration responsibilities. In some maps these differences is not known with sufficient accuracy, which leads to the display window of constant warnings appearing in the ARCS-compatible systems.
• Vector cartographic material ENC, issued in accordance with the standard S57 National Hydrographic Service in cartographic system WGS-84.
Devices determine the position and Map System
At the dawn of the emergence of electronic devices location mapping system has received little attention, as it is widely used system used special cards (for example, cards Decca). Later, these systems appeared output data mapping system but still not given due attention and positioning errors treated on account of the lack of accuracy of the system. However, with the proliferation of GPS mapping system to become acquainted closer. Position accuracy is not important, if the coordinates are in another mapping system. GPS satellites use mapping system WGS-84. However, WGS-84 is not a way out for all positioning systems due to the differences between electronic systems nautical charts and displayed maps.
ECDIS and Mapping System
These materials are used ECDIS ENC, created in the standard mapping system uses the WGS-84. Positioning devices connected to ECDIS should work in mapping system WGS-84. IMO requires that ECDIS filed alarm if the positioning device uses a mapping system that is different from the WGS-84. In practice, this requirement is impracticable, as standard, used positioning devices (IEC 61162, the previous NMEA 0183) does not include a message about the cartographic system. For this reason, classification societies endorse only those devices positioning interfaced with ECDIS, which can not be changed mapping system (ie, always WGS-84).
Note: The ability to verify the position of the mapping system - a relatively new feature receiver position. It was introduced in the standard IEC 61162-1 Ed2, published in July 2000. Only EPFS (eg GPS or DGPS), the certificate of approval which indicated 'IEC 61162-1 Ed2 (2000-7)', can provide ECDIS mismatch detection function mapping systems.
ECDIS and user selectable Local Mapping System
ECDIS allows the user to change overlooks the mapping system. This choice mapping system does not change anything for the process within the ECDIS navigation calculations or display process electronic nautical chart. But it changes the numerical values of positions displayed on the screen in the ECDIS user selected cartographic system. It is very convenient, especially if you prefer to build graphics with ECDIS on the traditional paper map.
Screen ECDIS (Electronic Chart Display and Information System) is divided into several areas. The status bar, which is always present at the top of the screen, basically displays the status of the equipment.
Rectangles at the right edge of the screen in the Information field. They are always present on the screen and give information such as the position of own ship served system alarm mode working station and the cursor position. The operator can display the data of their choice in one of the information fields, called sidebands. Lower unit information area is Area functions of the mouse and the left shows the current functions keys, scroll wheel and right mouse from left to right. 7/8 ECDIS screen occupies the area of electronic cards.
Mode vector and vector time
Planned route map name
Title pilotage data
Target data source
ECDIS can use the following types of cards:
• Maps ENC (vector) S57ed3
• Maps SM-93 (vector)
• Maps ARCS (raster)
In addition, the following data:
• The cursor (movable trackball)
• Planned route
• ELV (E-Line Vizier) and VRM (variable range circles)
• Symbol own ship with the velocity vector
• Purpose captured ARPA
Electronic maps in ECDIS
Electronic navigational charts displayed in the electronic map. There are two types of electronic navigational charts, which can be used in ECDIS:
• Vector format: S57ed3 ENC or CM-93
• Raster format: ARCS
Official paper maps can be replaced via S57ed3 and ARCS. Users need to check the current situation in his administration of the flag State and, in case of doubt, be used as a primary source of navigation information paper maps.
ECDIS combines chart and navigational information. It should be noted that modern navigation systems (eg, differential GPS) may provide a more accurate determination of the position than those used to determine the position in surveying some of which were obtained by electronic navigational charts.
Vector format S57
ECDIS is compatible with cards format S57 release 3 ENC. From this format ECDIS generates 'system ENC', = SENC, which is used for the actual action ECDIS.
When you open the card, it is displayed in the default scale, called scale compilation. detailed maps displayed in the e-card and may vary. You can zoom the map using the functions ZOOM IN and ZOOM OUT, zoom range 1:1,000 - 1:50,000,000.
Compatible with CM-93 format depends on commercial agreements. Some versions of this ECDIS compatible, and some - not. Compatible controlled safety device called 'dongle' ('key'). Format of the SM-93 generates ECDIS SENC, which is used for the actual action ECDIS. difference between the cards and the cards S57ed3 ENC SM-93 is that the card CM-93 were obtained from a private source and can not be used as a replacement for paper maps or under what conditions. To emphasize this fact, these cards in this guide are called 'Non-HO'.
ARCS Raster format
ARCS cards are digital reproductions of paper maps of the British Admiralty. They retain the same standards of accuracy, reliability and cleanliness as paper maps.
Increase map ARCS can be useful to increase the intricate details, but it reduces the density of the displayed data and can create a false impression of distance from danger. For this reason, it is possible to change the scale or 2x 1 / 2 with respect to the original scale chart paper.