In this day and age you would think that any boat owner would have little use of a paper nautical chart. But a chart is very useful and contains a wealth of information which may not be available on a chart plotter or computer display. Typically all charts will contain depth, sometimes called soundings in either feet, meters or fathoms ( one fathom equals 6 feet). Charts also show navigational markers, obstructions and other points of interest or hazards to mariners. Charts come in different scales and which is used will depend of personal preference and the area being navigated, a large scale chart for harbors and rivers and a small scale chart for passage planning or longer voyages offshore. A chart will have a scale along the top and bottom and these show latitude and longitude, horizontal along the top and bottom for longitude and vertical along the extreme left and right of the chart for latitude. Positions marked on a chart are always given as a series of numbers; degrees, minutes and seconds. It is also worth noting that one minute of arch, not to be confused with one minute of time is equal to one nautical mile with 60 seconds making up one degree. You can often find a scale elsewhere on the chart showing nautical miles and thus by opening up a pair of compasses to a desired distance measured on the scale it is possible to walk the dividers across the chart to find the distance between two objects. Assuming that we were cruising on a sailboat traveling at 5 knots and we knew where we were we could set the divers to five miles and mark our estimated position in one hours time as long as our course did not alter. Or we could find our distance off from the shore or other point by measuring the distance with the dividers and then referencing this back to the miles scale. It is also worth pointing out that latitude and longitude are measured north or south from the equator and east and west from the Greenwich meridian in London, England. For instance the position of the 59th street harbor marina in Chicago is at 41. 47' 30” North and 87. 34'51” West. Knowing your lat and long at anytime is a good idea as it unequivocally establishes your position which can then be passed onto the coast guard if you got into trouble and needed assistance. This is much simpler and less ambiguous than just saying “about 10 miles from the big white light house”. Also charts are an important back up should your electronics fail, knowing where you are at all times is less stressful and means that you are less likely to get into trouble or make mistakes especially when you are tired. One good practice is to update your position on the chart every 30 minutes or hour, if on a longer passage, noting not only your position but the time as well in soft pencil on the chart which can later be erased when you have safely completed your voyage. In fact you can also mark favorite fishing or gunk holing spots on the chart too so that you can easily get back to them at another time. Another way that charts come into their own is on passage planning. I like to lay the chart out and study my intended route, making note of any obstructions or places that I need to avoid, sure you can do this with a chart plotter but by the time that you have zoomed out to show your starting and finishing points all detail is lost, this is especially troublesome on smaller chart plotters. Once I have done the basic planning on the chart I can then enter way points into the electronics with confidence.
If you don't keep charts on board then I strongly urge you to do so and even if you do have some aboard it may be time to pull them out dust them off, brush up on your chart work, you might be glad you did.
Nautical charts can be obtained through the NOAA website which lists all chart agents.
West Marine and other boating suppliers may also often have charts although these will often be limited to your local area.
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