The modern version of the paper chart comes in two primary forms, the familiar CD-ROM which the computer uses and the solid state EPROM data cartridge that the Chartplotter uses. Sometimes the EPROM is referred to as solid state memory because it has no moving parts. In both cases the ROM stands for Read Only Memory, which means you cannot erase them. Data cartridges come in many forms. Most are called "chips" or "cards" due to their computer chip based architecture. The early chips were large and only held a few charts. Their speed, capacity and cumbersome size were all limiting factors.
Today things are different. Gone are the bulky cards of the past. The newest cards are about the size of a postage stamp. Recently the chips have grown in capacity to hold not only multiple charts, but now multiple regions. It is possible to have the entire west coast charts on a single chip. In the very near future we will be able to hold the entire world on a single chip! Also, with digital camera and generic memory becoming so popular, solid state memory prices have dropped down significantly. The CD-ROM based systems have also evolved to utilize the high capacity DVD format and do away with multiple CD-ROMs.
All chart plotters require electronic chart(s) of the area(s) in which you will be cruising. Many electronic charts are electronic copies of NOAA or other Government's Hydrographic Agencies, depending on charts for the area in which you will be cruising. The most basic chart plotters use raster charts. The more complex chart plotters use vector charts and some have the ability to use both. Raster charts are digital photographs of paper charts usually created at resolutions of 100 by 100 dots per inch (dpi) or greater. The charts are then programmed so that longitude and latitude positions can be calculated and stored on memory chips which can be plugged into a chart plotter. Since raster charts are digital photographs of paper charts, all of the navigational information is displayed exactly as it is on a paper chart. This is advantageous because the electronic chart is familiar and immediately understandable to the user. The disadvantage of raster charts is that zooming is limited, since zooming simply magnifies the picture but without additional detail.
Like raster charts, vector charts are also digital images of paper charts. The difference is that once the image is created it is then vectorized. Vectorizing converts the information in the image into coordinates that are then digitally stored. When a chart image is vectorized, the various types of information on the chart are stored in layers. For example, all of the underwater obstruction would be stored in one layer, the coastlines in another layer and onshore references in another. A chart plotter then uses the coordinates to build the chart on the screen. The user can then choose to display all of the layers or only some of the layers, so that the image on the screen is easier to read and use. Another advantage of vector charts is that they have the ability to be compressed prior to being stored, thus they take up 1/10th of the space of a raster chart. Since vector charts are digitally smaller than raster charts, more of them can be stored on a memory chip or disk, and they load significantly faster. Since vector charts are stored in layers, zooming will increase the level of detail, while not sacrificing image resolution.
Initially, vector charts received high popularity due to their small size, quick loading and the ability to be easily updated. However, the increased processing speed and memory size of today's chart plotters has reduced the difference in charts to the point that in some cases raster charts are preferred. In addition both raster and vector charts can be easily updated
The chart chips contain a pre set package of multiple charts in numerous scales. For C-Map, their charts follow NOAA chart areas. The charts on the chip cover the exact same area as the paper charts in the region. The advantage to using standard NOAA charts is that you can quickly switch from chartplotter to the corresponding paper charts. C-Map has recently stitched them together to form a seamless region.
One of the less mentioned issues is backwards compatibility. The C-map NT card or CF-95 was introduced in 1995; it was later revised in 2002 to the NT+ standard we see today. While these chips look the same, they won't always work together. The NT+ systems can read the NT chips, but many of the older Chartplotters cannot read the newer NT+ chips without a software update or on some units, a hardware update. In many cases even if the unit can read the larger chips, it runs very slow and has trouble with the increased chart resolution and detail with many of the new chip feature not showing up.
Navionics set their charts up in a different manner. They did away with the traditional paper chart areas and opted for seamless regions and depth contours. This allows for smooth scaling and scrolling between areas and makes it convenient for the user to see the navigational information for an entire region without conventional chart boundary lines. Navionics has the NOAA ranges defined also. It is important to note that while electronic chartplotters are very accurate, they should never be used without having proper paper charts available as a backup.
Navionics currently has 4 primary media types that are specific to the model. There are 5 chip types currently supported. For the most part the chips are standardized. The exceptions are the older MicroCharts and the ECharts. You cannot upgrade the software on older Navionics plotters to work with the latest cartridge designs such as CF, MMC and SD (2005).
One of the most common questions that people ask is about detail and coverage area. Many of the advertised areas do not cover all of the area in full detail. Instead, they contain a high resolution chart for areas where it is needed, such as a small harbor or channel. For the most part, the charts contain as much or more information than their paper counterparts. The latest cartography contains information about tides and current, marinas, service facilities, fuel docks and much more. Recently C-Map began adding increased detail on marinas. Some of the charts even list slip letters and telephone numbers.
With the increase in capacity and performance of the lower priced solid state memory and the increase in processing power, computers and chartplotters can handle much more information. Therefore, the latest electronic charts are generations ahead of the previous technologies. CD-ROMs and DVDs will continue to provide computers with cartography. Similarly, EPROMS will continue to evolve and be used by chartplotters. The future holds a merge of the computer and the chartplotter. This has begun with pc based trip planning software to be used with the chartplotter. There are also chartplotters that now function like computers such as using CD-ROMs. Already the line between the two has blurred. Look for increases in capacity and data with better graphics and feature sets that rival the paper based content of today.
For most of modern navigation history, the paper chart has been the primary source of information.
Only recently has the computer become a strong player in the market. Chart plotting software and hardware
is beginning to rival the speed and ease of the traditional paper chart. Position finding technologies
such as LORAN and GPS (Global Positioning Systems) have made navigation easier and more exact.
