CHAPTER 2. ELECTRONIC CHARTING

ALL ABOUT ELECTRONIC CHARTING

Most chart plotters universally now incorporate GPS, or conversely are included within GPS units, and are effectively position-fixing devices for many. The chart plotter is essentially a display with processor that decodes the data on the chart cartridges for display on the screen. The information is often layered so that chart areas can be expanded. The lights, buoyage and contours can be called up as required. There are many functions and stored data available. They can include tidal predictions; sun and moon rise and set, Navaids such as lights and buoys (10,000 plus items is typical), waypoints and routes (1000/20 is typical). DSC radio interfacing is also possible showing the location of a vessel in distress. One important feature is sets that use standard chart cartography as some use proprietary software that may not
be easily obtainable. There are many features to consider that include drag and drop waypoints, active route waypoint insertion and deletion, and the ability to store routes, and fast redraw times, typically 0.5 to 3 seconds. Cartography features should include clear chart scale indication, clear direction indication when not in North-up mode, an indication when over-zoomed, good buoy visibility and identification, clearly visible and identifiable land features and contours, the use of standard labelling conventions on features, the display of drying heights, the ability to edit contours and shaded depth contours. One important factor is the ability to update and also some identification when the chart was last updated, similar to paper charts. It is important that any unit be user friendly, and has intuitive controls, menus, soft keys and dedicated keys.

CHART PLOTTER DISPLAYS

Systems now use high-resolution monochrome (gray) LCD displays, or full color active matrix TFT (Thin Film Transistor) displays. Screen display quality or resolution is determined by pixels, i.e. 480 x 350. The greater the number of pixels, the greater the resolution, and the price also increases. Power consumption is typically 6W (0.5 amps). To get the most from dedicated plotters or computer-based software plotting, make sure you read and understand the manual and practice. Trying to learn while under way is both dangerous and distracting. There is a trend in larger motorboats and sailing yachts to have PC based systems with remote sunlight viewable displays, for pilothouse and fly bridge. Many displays are flat-screen LCD types with SVGA resolution, and external standard ones are waterproof to NEMA 4 standard and are rated up to a brightness of more than 1,600 nit which is some 1000% brighter than a laptop.

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