First off, no matter where you are going, you will need to do some planning. In the planning stage you will draw the course lines on your chart from the departure point to the arrival point. These two points may not necessarily be your berth positions. The departure and arrival points, in most cases, will be the buoys that mark the entrance to the harbor, channel, inland waterway, or traffic lane for that port. For coastal routes you will usually have several waypoints along the way as you proceed from buoy to buoy, avoid hazards, and go around islands, points of land, rocks, or reefs.
The first part of the preparation stage is pre-departure knowledge of distances and courses you'll be sailing.
On the chart, I like to highlight important information with different colors, making it easy to use while underway. For example I use yellow, red, and green for the important lighted buoys; I also use yellow to highlight navigation channels and ranges, depth contours, and the variation in the compass roses. I also like to draw additional latitude and longitude lines to make the plotting easier and highlight the latitude and longitude degrees and minutes on the edges of the chart. I can gussy up my navigation chart all I want as I use a new chart every time I go out. The old charts along with the deck log are filed away after the voyage is complete.
Now, if you are using one of the computerized navigation and electronic charting programs, this planning stage is easily done. Once finished it can be printed out and the waypoints uploaded into the GPS with a few clicks of the mouse. I would also highly recommend that you plot these points on a regular paper chart for use while underway. If you use the ChartKit charts, most of the coastal routes have been plotted and annotated with the course and distance between prominent buoys and waypoints.
Keeping track of navigation aids makes life aboard less stressful in harbor and channel situations.
Professional work in the chart room can save the need for professional work in the boatyard later on.
Obviously on a small boat with minimum crew, the navigator and the captain of the vessel can be the same person, while a family member or close friend acts as the crew and helmsman. In this type of situation the voyages are usually short, with the exception of the long-range cruising families. Whatever the crew situation, it is always best to take a professional approach when it comes to navigation and seamanship.
For navigation while underway, the three basic principles of Dead Reckoning must be followed:
|A DR can only be started from a known position|
|Only true courses actually steered are used for the DR track|
|Only the speed through the water is used for calculating the distance traveled.|
A DR position must be plotted every hour on the hour, at every change of heading or speed and at every fix. Until a fix is obtained, you must continue plotting the DR position from the preceding DR position. You may plot an Estimated Position (EP) using predicted set and drift or perhaps a single Line Of Position from a depth contour or bearing off a buoy, but the DR will continue from the DR position and not the EP.
Arriving in an unfamiliar harbor always requires prudence and often patience.
In addition to Dead Reckoning, by plotting on the chart by means of course and distance from a known location, you can also do DR by computation. The various methods of DR computation by calculation are collectively called the Sailings. Of the eight different types of Sailings listed by Bowditch, the ones most commonly used are Great Circle and Mercator. For voyages of less than 200 miles, either one will give accurate results, but the Mercator calculations are much simpler. But, for long distances you will need the accuracy of the Great Circle calculations. For those of you who are interested, the Sailings are discussed at length in Bowditch. I would suggest that you take the Advanced Piloting course offered by the US Power Squadron if you want to know more about these methods of DR calculations. Several computer software programs also make these types of DR calculations for you as part of their log-keeping options and for serious navigators they are well worth considering.
Illustrations by Mark Smith from The Annapolis Book of Seamanship, by John Rousmaniere, Third edition (Simon & Schuster, 1999)
Last edited by administrator; 08-01-2006 at 04:16 PM.
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