The intercept method

Choose an assumed position near your dead reckoning. From it, for the time of the sight, compute the altitude and the azimuth at which the body would appear, by the sight-reduction tables or by the formula. Compare the computed altitude with the observed one: the difference, in minutes of arc, is the intercept in nautical miles. If the observed altitude is the greater you are nearer the body's geographical position: plot the intercept from the assumed position towards the azimuth; if the computed is the greater, away. Through the intercept's end draw a line at right angles to the azimuth: the position line.

Every sight, of any body at any time, reduces to that one picture.

An observed altitude greater than the computed one means the intercept is plotted which way?
The position line is drawn how, relative to the azimuth?

Show the answers
  1. An observed altitude greater than the computed one means the intercept is plotted which way? Towards the body's azimuth A greater observed altitude means you stand nearer the body's geographical position.
  2. The position line is drawn how, relative to the azimuth? At right angles to it, through the intercept's end Every point of the line is at the same distance from the body's geographical position.

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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