Electronic Chart Displays and Formats

How They Work
In the last decade there has been tremendous improvement in both position fixing devices like GPS, and in the ability to store and recall cartographic information (charts). It is now possible to buy a fixed-mount GPS which can display detailed charts for about $500. Hand-held GPS receivers also have chart displays, and rival the fixed-mount models in their capabilities. There are great advantages to integrated GPS/chart plotters:

1. Boats with limited navigation areas are now able to display charts covering many hundreds of miles of coastline and dozens of charts, at a variety of scales.
2. It is much easier to enter a waypoint into a GPS, since it is done by picking the desired point on the chart visually, without typing in coordinates. Routes are created by simply stringing together waypoints, or by creating waypoints on the fly.
3. It becomes easy to understand your boat's position relative to hazards like land masses and shoals, your intended course, and your destination. The position of your boat as shown on the chart is as current as the last position fix from the GPS. Instead of spending lots of time plotting your position on a chart and failing to keep a good watch, you can concentrate on your surroundings from the helm and your radar.
   

What should I use to display the charts?
There are three popular methods of displaying electronic charts:

Dedicated GPS/Chart Displays
With or without an integral GPS, these products house high-resolution LCD displays in water-tolerant enclosures. They are designed to be mounted in wet (not drenched) locations. All use some combination of C-MAP, Navionics, or a proprietary database stored in a bewildering variety of chart cartridges. We really like this approach, and think that it makes sense. User interfaces have been refined to the point that these are among the easiest-to-use marine electronics.

Combination Electronic Displays
Most boats don't have room for a dedicated display for every function on board: radar, fishing sonar, charting, instrument repeaters, etc. Frequently one primary display requires most of your attention, while other functions are far less important. Garmin, Furuno, Raytheon, Si-Tex, Lowrance, and others allow you to display two or more functions on a single display. For example, the Garmin GPSMAP 185 Sounder has a GPS, chart plotter, and fishing sonar in one package. Most radars now have add-on chart readers which let you toggle between a radar image and chart image on the same display. This technology is available for both CRT and LCD displays.

While this approach saves space, and is less expensive in some cases, we are not big fans of installations where the chart operation control is remotely mounted from the display. Frequently you need to look at on-screen information, yet your fingers have to enter data or select functions off to the side. We prefer to have all data-entry keys right next to the display. We also find that some of the combination product user interfaces have not kept up with the dedicated products.

Laptop and Desktop Computers
The last five years have seen an explosion in the number of PC software programs that display chart information using the input from a GPS. Programs from Nobeltec, Nautical Software and Maptech® let boaters put their PCs to work on board. In general, these programs use raster charts from private sources or NOAA/Maptech®, and offer the most "chart like" appearance on screen, especially when used with a PC that has a high-resolution, active-matrix display. Larger boats may use a desktop PC and a large color display, but this is too power-hungry and takes up too much room on smaller yachts.

While it is tempting to bring a laptop computer on board and to use its large display and extensive data-entry abilities (the keyboard and mouse) to manipulate data, you must also contend with several challenges:

1. Many boats don't have comfortable places to work with a computer which allow it to be protected, seen, and typed on at the same time.
2. Laptops are notoriously water sensitive, and can be ruined in one regrettable, wet moment.
3. Laptop displays are frequently hard to read in varying light conditions, and hard to use at the helm unless your helm is specifically arranged for them.

Chart Providers
So where do you get all this neat chart data so you can pop it up on your new cartographic display? There are several possibilities:

Charts on a Chip
Many different chart formats are available on memory cards, which are fast, reasonably waterproof, and not subject to vibration problems when your boat is pounding toward Bimini. Offshore charts are provided by Navionics and C-MAP, while inland data can be supplied by Garmin, C-MAP, and Lowrance. There are many formats: We stock over 10 different cartridge series. Each cartridge holds between 6 and 80 charts, and new mini format cartridges (C-card from C-MAP, micro G-Chart from Garmin, and NavChart from Navionics) may hold several hundred charts. Prices range from $100 to $400 per cartridge.

Since the data is in vector format, it does not look like conventional paper charts, although CMAPNT charts look darned close when viewed on a color display. In color or monochrome, vector charts tend to be simpler and look less like familiar paper charts than the other electronic chart format, raster charts. However, they have some substantial advantages over raster charts:

1. Very fast screen update rates combined with greatly reduced storage and processor requirements due to the vector format.
2. The ability to change from very large to small scales while still being able to read text and identify icons and other features (fonts are constant size).
3. Charts are seamlessly integrated so that you don't run to the edge of a chart and have to pull in entirely new map data.
4. Chart information is stored in layers so that data may be selectively shown or removed from the image, and chart attributes can be queried for incremental information.

At least two potential problems exist:

1. There are at least ten chart formats from several vendors which make it next to impossible for a retailer to have the right chart for your particular device in stock. Chart data is frequently out of date.
2. The chart images don't look like conventional NOAA paper charts.

Downloadable Vector Charts from a CD-ROM
This is the newest category, and already Garmin, Magellan, and Lowrance have GPS receivers which can download map data from a CD. You can select the geographic area, and in many cases, the type of information of greatest interest to you (points of interest, marine aids to navigation, road networks, hiking trails) until it fills up the memory in the GPS. Some allow you to download any portion of the CD, while others are on a "pay per view" basis where you have to pay to unlock each geographic areas. We see great potential in this storage method.

Raster Charts on CD-ROM
Raster charts are electronic files made by scanning a paper chart. NOAA has teamed up with a private distributor (Maptech®) to bring their library of 1,000 charts to the public. The charts are stored on CD-ROMs with high memory storage capacity and tolerance for wet environments. Each CD-ROM stores up to 50 NOAA charts and inset charts of harbor areas. The chart images, when viewed on a color LCD or CRT display, look just like the paper source map. In addition, other national Hydrographic Offices are beginning to use the same raster format, so that the software is compatible with foreign chart providers.

The current software available for displaying raster charts is dramatically better than that available even two years ago. It is easy to use, utilizing most of the common software interfaces that make newer software operate consistently. Chart re-draw speeds are greatly improved, so that zooming and panning are not chores. And, obviously, computers are dramatically better each year, with more speed, better displays, and almost universal inclusion of CD-ROMs in all portable models.

Software features are rocketing ahead, as well. Among the more impressive are the new mapping engines, which make raster charts practically seamless, and make it easier than ever to select the right chart for a given scale. Another great feature is the integration of tide and current information with the chart presentations, so you can see where the current will be ebbing or flooding on the next leg of your voyage.