Navigation and Raising a Degree
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Which shows you by the use of your compass, how far you must sail to raise a degree, and how much you depart from the Meridian in doing so.
Furthermore, because there are some that desire to know the alteration of a point, so that in running on a course, they know when they have raised or laid a degree. For in sailing due South, and keeping to one Meridian, you raise the Pole after 60 miles, and lay the same after sailing 60 miles due South. But in sailing East or West, you neither raise nor lay your Pole, but only alter your Meridian at a degree every 60 miles at the Equinoctial, or less depending on your Latitude. Whereas, in sailing any other point you alter both your Pole and your Meridian. Wherefore I will list for you, when sailing upon any point, how far you must sail to raise or lay one degree North or South, and what distance you have departed from your Meridian in doing so.
Units
But here is one thing to be noted, that some charts measure distances in land miles, being only 8 furlongs or 5280 feet; furthermore charts of far-off land being most commonly made in Destiny, they allow for every degree only 17 1/2 of their leagues, at 32 furlongs apiece. But as I take is, we in Carzala should allow 60 nautical miles to one degree, and there being 3 miles to a league, wherefore 20 of our leagues should be one degree. A nautical mile contains 6080 feet, which is not a good number of furlongs, chains, or rods, but it is exactly one minute of Latitude, and thus better than any round number of paces.
Raising a Degree of Latitude
Now we list the distance to travel, and the Meridial departure which is the number of nautical miles travelled East or West, to raise one degree of Latitude on various headings. The values are given for sailing North and East, but the same may be used in any other quadrant.
- Miles to Raise 1° Latitude
| Point | Distance to Lay 1° |
Meridial Departure |
|---|---|---|
| N | 60.0 | 0.0 |
| NbE | 61.2 | 11.9 |
| NNE | 64.9 | 24.9 |
| NEbN | 72.2 | 40.1 |
| NE | 84.9 | 60.0 |
| NEbE | 108.0 | 89.8 |
| ENE | 156.8 | 144.9 |
| EbN | 307.5 | 301.6 |
| E | -- | -- |
And again, having travelled 60 nautical miles which is 1 degree in a Great Circle, we list the number of minutes of Latitude that have been raised, and the nautical miles travelled East or West.
- Minutes raised after 60 miles
| Point | Minutes Raised |
Meridial Departure |
|---|---|---|
| N | 60.0 | 0.0 |
| NbE | 58.8 | 11.7 |
| NNE | 55.4 | 23.0 |
| NEbN | 49.9 | 33.3 |
| NE | 42.4 | 42.4 |
| NEbE | 33.3 | 49.9 |
| ENE | 23.0 | 55.4 |
| EbN | 11.7 | 58.8 |
| E | 0.0 | 60.0 |
Raising a Degree of Longitude
While mariners all know that the distance of a degree of Longitude is greatest under the Equinoctial, where is equals the degree of Latitude, it is not so common to know the distance to travel to raise a degree of Longitude as various Latitudes. Wherefore I have listed these values for you.
- Miles to Raise 1° Longitude
| Latitude | Meridial Departure |
|---|---|
| 0° | 60.0 |
| 10° | 59.1 |
| 20° | 56.4 |
| 30° | 52.0 |
| 37° | 47.8 |
| 40° | 46.0 |
| 50° | 38.6 |
| 60° | 30.0 |
| 70° | 20.5 |
| 80° | 10.4 |
