The running fix

The Sun is often the only body up, and a single line is not a fix. Take a Sun sight in the morning, when its azimuth is well to the east; run on; take the noon sight for latitude. Advance the morning line by the course and distance run between the two times, the log giving the distance and the compass the course, both corrected, keeping the line's direction; where the advanced line crosses the noon latitude is the running fix. Its accuracy is the accuracy of your run: a current you did not know about moves the whole picture.

The same transfer serves any two sights hours apart, by day or by night.

The morning Sun line is carried to noon by what?
What limits the accuracy of a running fix?

Show the answers
  1. The morning Sun line is carried to noon by what? The course and distance run between the sights The line keeps its direction and moves with the vessel.
  2. What limits the accuracy of a running fix? The accuracy of the run between the sights An unknown current or a log error moves the advanced line with it.

The twelve evenings

  1. The celestial sphere
  2. The sextant
  3. Time and the almanac
  4. Correcting the altitude
  5. The noon sight
  6. Latitude by Polaris
  7. The navigational stars
  8. The intercept method
  9. Plotting the position line
  10. The running fix
  11. The Moon and the planets
  12. The day's work

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