• Any discussion of navigation publications should begin with what has to be considered the very foundation of navigation, the chart. Nautical Charts A Brief Introduction to Nautical Charts Nautical charts are essential for planning and safe navigation while underway.  In the United States, nautical charts are the responsibility of NOAA’s Office of Coast Survey.  A nautical chart details information regarding water depths, bottom contours and characteristics, shoreline contours, hazards and dangers to navigation, positions and characteristics of aids to navigation, anchorages, as well as a wealth of additional information.  Charts may be obtained in either printed or electronic versions. In many cases free of charge directly from NOAA (or the…

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• A bearing is the direction to an object or location, expressed as degrees relative to a reference point or direction. In piloting, three “types” of bearings are used most often. Related Pages Bearings and Directions – TVMDC True Bearing A bearing expressed in degrees true uses true north as the reference point. True north is found by drawing a line between the North Pole and the South Pole, known as a line of Longitude. The direction along this line to the North Pole is “True North” and is labeled as 000° (degrees). The bearing to the object is determined by calculating the number of degrees clockwise from 000° to the…

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• What is an estimated position Dead reckoning uses only course, speed, time, and distance to establish an approximate position. Two or more lines of position are required for a fix of a vessel’s actual location. An estimated position is anything in between. As a result, it may be a DR position with set and drift taken into account. It may also be a single line of position in plotted into a DR location. While estimated positions are approximate, they are more accurate than a simple DR position. Chart Notation The plotting symbol for an estimated position is a square with a dot in the middle. In the example above there…

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• Learning Objectives Recognize factors contributing to DR vessel location “inaccuracy.” Comprehend what a line of position (LOP) is. Understand steering error Define Leeway Describe Set and Drift. Explain Course Made Good and Speed Made Good. Establish an estimated position using DR and a single line of position. Resolve set and drift by comparing a DR position with a Fix. Determine course to steer to compensate for known set and drift. Factors contributing to location inaccuracies A navigator must always keep a running DR plot. As discussed in the lesson on Dead Reckoning a DR position should be updated and plotted at a minimum of hourly and at any speed or…

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• Where am I? Where am I going? Dead Reckoning is the systematic determination of present position, based upon course and distance travelled from a known location. It is a way to find an estimated future vessel position. In fact, possibly its most important use is projecting into the near future to see hazards. As a result, avoiding dangers along the way to a destination. In other words, dead reckoning shows the best route to follow to arrive at your destination safely. Variations on a name No one is quite sure where the term “dead reckoning” came from. It may be a shortened version of the phrase “deduced reckoning,” which does…