Plotting the position line

A position line says only that you are somewhere on it. On a plotting sheet, a blank chart whose latitude scale is drawn for your latitude, mark the assumed position, draw the azimuth through it, step off the intercept towards or away, and draw the line at right angles. Label it with the body and the time. Two lines from two bodies at nearly the same time cross at a fix; three give a cocked hat whose size tells the honesty of the sights. The sheet's longitude scale shrinks with the cosine of the latitude; the sheet's own graduation takes care of it.

Transfer the fix to the chart by its latitude and longitude, never by distance from the sheet's edges.

A single position line tells you what?
Three position lines that do not meet in a point form what?

Show the answers
  1. A single position line tells you what? That you are somewhere along it A second line, from another body or another time, is needed for a fix.
  2. Three position lines that do not meet in a point form what? A cocked hat Its size is a measure of the sights' consistency.

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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