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Chart Plotters
Marine Articles >Boat Electronics > Chart Plotters
An Introduction to Chart Plotters
Chart Plotters are one of the most fun and helpful electronics in the marine industry and yet it can be a tiresome process trying to decide which chart plotter you need. An Introduction to Chart Plotters is written to introduce boaters to chart plotters and provide them with information to help them choose the write chart plotter. To the right are articles on specific chart plotter models as well as a link to Go2marine.com where you can see all of the chart plotters they carry.
Chart Plotters at Go2marine.com
A chart plotter is a computer that has or interfaces with, GPS or Loran and displays a vessel's position on a corresponding electronic chart. The last three decades have seen an evolution in chart plotters from "box-like" bi-colored machines using Loran "C" lines, to colored hand-held GPS units and large monitor display units with internal processors that rival the most modern of home computers. Although chart plotters were initially used by the military and the commercial marine industry, they are now common place on recreational vessels.
Chart plotters have revolutionized marine navigation by replacing the need to "shoot" the stars or an azimuth, with the conversion of a vessel's GPS or Loran coordinates into an easily understood picture on an electronic chart showing the vessel's position and course in relation to its surroundings. This improves the navigator's situational awareness, his ability to correlate his vessel's position in relation to surrounding land, channel boundaries and various navigation aids and other vessels. The more complex chart plotters improve situational awareness with detailed charts, aerial photographs of significant areas, the ability to use waypoints to plan a voyage, mark significant areas, and calculate distances plus time of travel. There are also chart plotters that have a guide book built into them and provide a list of onshore attractions as well as the locations of public docks and anchorages and fuel docks. Some chart plotters also provide tidal and lunar activities. There are also chart plotters that can interface with other navigational systems, like radar, speed, depth and wind instruments and water temperature.
 A chart plotter's screen is one of the most important parts of any chart plotter, no matter how advanced a chart plotter is, if you cannot see the screen it is useless. Chart plotter screens and monitors come in a variety of sizes, resolution and effectiveness in different lighting conditions. Currently the most available screens are monochrome LCDs which provide moderate to great visibility in differing light conditions encountered in and outside. If you plan to use your plotter outside in direct sunlight, screens with a specified brightness of 1400 nit or higher are your best option. If you plan to use your chart plotter inside or in subdue lighting, color CRT and LCD screens are your best bet.
Types of Charts
Like raster charts, vector charts are also digital images of paper charts. The difference is that once the image is created it is then vectorised. Vectorising converts the information in the image into coordinates that are then digitally stored. When a chart image is vectorised, 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.
Although trying to decide which chart plotter is best for you can sometimes be a painstaking and confusing task, here are four factors that can help. First, you need to determine your basic navigational needs? Do you need a chart plotter that needs to be able to interface with other navigational systems, such as your radar, autopilot or instruments? Do you need the ability to place waypoints, markers and or plan voyages? And if so, how many waypoints or journeys do you want to be able to save on your machine? This will help you determine whether or not you need a chart plotter with a large amount of memory. You also need to decide whether you need a chart plotter with one or multiple outputs. If you need the ability to view your chart plotter in more than one place then you need a chart plotter that can support two or more screens.
Secondly, you need to decide whether you need a stationary or portable / hand-held chart plotter. Hand-held chart plotters tend to have smaller screens and depending upon your vision (and age), can be a little more challenging for you to see the chart details. In addition to having larger screens, stationary chart plotters tend to have a few more function buttons and thus be a little easier to access programming menus. Stationary chart plotters often support additional screens which is essential when mounting a second screen elsewhere on the boat such as on the flying bridge. Obviously waterproof integrity is also an issue for any chart plotter used outside the cabin. Based on the above answers you should be able to decide on whether you want a small hand-held chart plotter that is portable and can be easily moved to different areas of the boat or even between boats, or a larger stationary chart plotter with repeater screens for different areas and perhaps purchase different chart plotters for each boat.
The third factor is deciding on what type of screen you need. If you plan to use your chart plotter outside or in subdued sunlight, you need to ensure that the plotter you buy has good visibility under direct sunlight. In deciding what type of screen you want, you also need to think about where it will be placed. How much actual room you have available is important. This will dictate how big of screen you can fit into the space. As mentioned above, where you are going to place your chart plotter also determines whether you need to purchase a plotter that is weather proof and/or splash proof.
The fourth factor in helping determine what type of chart plotter you need is chart preference. Before buying a chart plotter it is important to decide whether you want to use raster, vector or both types of charts. In addition, some brands of chart plotters only use proprietary charts produced by the manufacture of the plotter. Other plotters support third party charts. Depending on the areas of cruising, it can be prudent to look at a sample of the charts that will be available for the different chart plotters. Also certain plotters are compatible with third party software for tides and currents as published by NOAA, as well as Windows compatible software for trip navigational planning on your PC.
Hopefully these factors will enable you to narrow your search down to a few models of chart plotters that will best meet your needs. However, even though chart plotters are an amazing benefit to marine navigation, they do not replace the need for paper charts and the ability to navigate without them. We must remember that chart plotters are machines and as such they can develop a problem at anytime and leave you needing paper charts and navigational ability to safely get to port to have your chart plotter fixed.
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