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Chartplotters Explained II

I will start with this subject since it is foremost on most boaters minds. First of all, we must understand that a chartplotter is a display of a chart. The GPS is a sensor which is responsible for putting your boat on the chart. A GPS sensor outputs LAT/ LONG, COG, SOG. This is the little mushroom or hockey puck on your arch, hardtop or rail, or sometimes built right in. The chartplotter is your most often used device on most boats. Basically, if you can look on a map and find your way, then the chartplotter will get you there on the water. Let me also mention some of the things that a chartplotter does not do: Keep you from running aground. Steer your boat. Make dinner plans. It is useful for accomplishing all three of these, but it requires proper operation.

In other words, a chartplotter is designed to enhance your awareness, not replace it. Know your boat and the waters. When in strange or nervous waters, make sure your electronics work for you. and that you know how to make them work for you.

It is important that you practice with your equipment every time you use your boat. That way, you are not pulling out the book when you really need to pay attention to your situation.

It has been said that boating is hundreds of hours or boredom punctuated by moments of complete panic. A chartplotter enhances your awareness of your situation, whether boring or beautiful. Having a good sense of how to use it makes it useful in an emergency.

The basic function of a plotter is to tell you where you are and where you’re going. When you first turn it on, it may take a few minutes to acquire a FIX. this means that it has locked onto at least three GPS satellites and has a position fix.

Once locked, the GPS sensor outputs Latitude, Longitude, Course and Speed. and an icon of your boat appears on the chart. You can zoom in and out to see greater detail or a wider area.

Your latitude and longitude are normally shown on the screen in a box. Often, course and speed, that is COG and SOG are also shown in little boxes. Knowing your lat and long is important. COG means Course Over Ground, which is position based direction of travel. Your lat and long are this, then this, then this, so you are traveling southeast.

SOG means Speed Over Ground and the is your position averaged speed of travel.

To know where you are going, you must first chose a destination. I like Saugatuk. So on a typical chartplotter, I would place my cursor on the chart at Saugatuk. When planning a trip, I zoom out until I can see my destination, across the lake. then I zoom in to the entrance of the harbor to place my cursor precisely where I wish to go.

Most plotters have a “GO TO CURSOR” function. Once activated, the plotter draws a line from my boat to the destination. When I see this line, I know I have entered a destination into my plotter.

Going to the cursor is great because it can be done quickly and spontaneously changed. But when you are cruising on vacation you may wish to plan your trip in advance.

Waypoints are the key to this. By entering waypoints into your chartplotter, you can choose from a list of destinations. Waypoints can be put in sequence to create a route.

The best example of this would be Wind Point. To get from here to Milwaukee, just go due north, but don’t forget to go around Wind Point, in Racine WI. There is a beautiful lighthouse there, but be aware that it marks shallow water.

So in order to go to Milwaukee from here, you must go North east to a point off of Racine and then turn Northwest toward Milwaukee Harbor entrance. To do this you create a route in your plotter consisting of two waypoints.

Routes and waypoints can and should be saved to memory cards. A route can consist of many waypoints.

Approaches can be set up for navigating in low visibility. Make a waypoint out about a half a mile from the harbor entrance and the another close in. By placing these two waypoints at a bearing to the entrance, you can put yourself on course to enter the harbor.

The best chartplotter in the world is no good without charts. Two companies compete in the consumer space with chips, C Map and Navionics. Raymarine uses Navionics, NorthStar uses C Map, Furuno uses either and Garmin uses Navionics lite. The world of electronic charts is exploding right now.

Furuno 3D has set a new standard for charts, with continuous zoom and zero redraw, but the charts are limited in this area (Great Lakes) right now.

The Department of Defense has published the paper charts in electronic form,that is scanned paper charts. These are called Raster Charts. The DOD has also published about 65% of the USA in Vector charts. These are the really cool, scaleable charts like C Map and Navionics.

There are many software packages that you can buy to turn your laptop into a chartplotter. Of course, you need a GPS sensor for your laptop in order for it to work, or you can get position data from you existing navigation equipment on the boat, by plugging you laptop, the GPS data, through the serial interface, USB or ethernet. No matter which chartplotter you choose, navigation using electronic chart is both simple and complex. Like many things in life, there is more to it then meets the eye. I will not be covering operation of chartplotters today, but let me just say that if you enter a destination from your slip to say, Holland, the chartplotter draws a line from your slip to Holland. This line goes right through the rock wall and your neighbor’s boat. If you try to drive that line, you will most assuredly run aground.


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