III. Navigation
Navigation is the single most important aspect of shipboard operation - as without proper, thorough and disciplined navigation and log-keeping the ship and it’s crew will not survive a single night out at sea. For this reason, the job of navigating the ship is typically the responsibility of highly trained and experienced officers - the Captain, First Mate and Lieutenant. Enlisted personnel and non-commissioned officers will provide assistance and man the sails, battens and lines as directed.
Navigation is accomplished with a series of instruments and charts. The instruments include day and night telescopes, a quadrant, navigational scales and rulers, protractors, dividers and writing instruments. These instruments are used to lay out a course on navigational charts which show an approximate arrangement of the coastline. These charts indicate important landmarks such as lighthouses, towns and natural features such as rock formations and hazards such as shoals. These charts also show the water depth and horizon height at a given location. A skilled navigator could then be able to determine the following with some calculations:
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Water Depth. When near the coast, drop a weighed 30-fathom long sounding lead into the water and then pulling it back out once it had touched ground. This depth is compared against the stated depth on a navigational chart as one of the data points to verify the ship’s location.
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Distance to Shore. Check how close the shore is to the horizon as this compares to the navigational chart or how tall a 100-foot lighthouse appears in a telescope. This distance is used to determine what the water depth at the ship’s current location should be at a given location as indicated by navigational charts.
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Sailing Speed using a common log. This is a rope with a wood dowel on the end, and the length having a series of equally-spaced knots. The rope is dropped into the water and the navigator will count how many knots unroll from the coil in a given amount of time (such as an hourglass or gnomish pocketwatch). The number of knots determines the speed of the vessel.
Using the information above, a navigator could determine that the ship is on course, or determine how accurate the current heading is and make adjustments as required. The navigator also keeps a detailed log of the ship’s current location upon verifying this information, which could then be used for any additional corrections as the ship continues on it’s voyage.
Marines may be able to make estimated calculations on the distance to shore during an amphibious assault or weapons ranging for shore or anti-ship bombardment by employing some rudimentary knowledge of shore navigation and distance calculation.
Deep-Sea navigation is far more complex and beyond the scope of further discussions for this manual which is intended for recruits entering into service as enlisted personnel.