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All navigation software programs prominently display warnings concerning reliance on electronic navigation systems alone. The rule here, as always, is common sense. Any system, electronic or paper, is vulnerable. Whether you consider paper charts, sextant, and compass to be your primary system, and your computer and GPS as the backup system, or vice-versa, is moot. Having redundant systems is reasonable and necessary when life and property are at stake. Perhaps more than any other factor, the type of electronic charts you will want to use should determine the navigation equipment or software that you will own. Consider that:
Proprietary charts may cover some geographic regions better than others, and some regions not at all. You can check out this article, though somewhat outdated, that covers some of the programs for Electronic Charting. |
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Vector chart information is stored as data in a database. The charts are labor intensive to create but data are stored with intelligence that the chart plotter is programmed to understand. Therefore the plotter can selectively display and react to information. For example if your GPS plotter is plotting your position on a vector chart, it could warn you when you are approaching too close to an underwater hazard. And it can zoom in and out on charts without distortion. Most manufacturers of computer charting software are gearing up so as to be able to display vector charts. In contrast, Raster charts are stored as images. The computer does not know that an image may be a navigational aid, or a navigational hazard. For raster charts to be useable by marine software, at least a grid of latitude and longitude information would need to be mapped to the image. Raster charts are easier to produce because they can be created by scanning existing paper charts. This is being done by the U.S. National Ocean Survey (NOS) and the British Admiralty's Hydrographic Office. Maptech (Resolution Mapping, Inc.) also produces raster charts. To use these charts, marine navigation software needs to have access to their proprietary formats. An alternative to using these formats is using self-scanned charts made by a home or professional scanner. This allows flexibility and cost reduction but also must be done with understanding of risk. The most important factor to take into consideration when purchasing a computer based electronic charting system is to make sure that the program can access more than one company's charts so that, in case the chart company disappears, you are still able to use your software with somebody else's charts. |
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| Chart details stored as intelligent data that can be selectively manipulated | Chart details stored as images |
| Proprietary formats, major producers are C-Map , Navionics, Livechart, Transas | Proprietary formats, major producers are NOAA, British Admiralty, Maptech, Canadian NDI. Possibility to scan own or use shareware charts inexpensively |
| Normally used by GPS plotters and specialized electronics equipment and high powered PC professional ship navigation equipment. | Normally used by PC navigation software |
| Charts are labor intensive to produce; require relative small amount of disk storage space | Charts are relatively easy to produce; require larger amount of disk storage space than vector |
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