What is intercept method or Marc St. Hilaire Method to find noon position of ship or position line?

General Rules

Marc St. Hilaire Method may be used at any time, but owing  to the more rapid change in azimuth of the heavenly bodies when  on or near the meridian, the best results are obtained when the  object is, say 20° or more from the meridian. If the object is on the  meridian use D. R. Latitude and Declination, and if near the meridian, use also the ex-meridian augmentation in computing the  zenith distance and hence the calculated altitude.

Rules for Solar Observations

We require :

1. The sun’s westerly hour angle (t), which is the ship’s astronomical apparent time.
2. The latitude of ship.
3. The sun’s declination.
4. Latitude difference declination (Lat. 1 DecL).
5. Equation of time.
6. True altitude.
7. True azimuth.