Sailing

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As Versegelung in which is nautical and navigation correction of a measurement constellation referred to when it is done on a larger time interval to a correlated measurement.

In the location determination (see also astronomical position line ) have the measurements verse gelt be because the ship between the measurements of the elevation angle moved. The reduction is calculated by multiplying the distance covered by the curvature of the earth (only the component in the direction of the observed star is relevant). When measuring two different navigation stars, the second measurement is sailed to the point in time of the 1st, in the case of three stars to the middle point in time.

In nautical practice, the sails can be omitted if, instead of a third star, the first star is measured a second time and the two angles are averaged. This " bracketing " is particularly useful in aviation , where a mathematical sail would be too costly due to the high speed.

When determining the location by means of the sun , a greater time difference (2-3 hours) is necessary in order to avoid grinding cuts between the two base lines. Because of the long distance covered, the sailing correction would be too imprecise here, which is why the second position line including the ship's location is shifted graphically (on the nautical chart ) to the location of the first measurement. To do this, you use the ( cast ) route estimated with a compass and airspeed indicator (see also dead reckoning ).

If the solar observation is combined with other stars visible during the day ( moon , Venus , bright stars) to save time, the process of sailing is to be carried out as with the star method mentioned above. The accuracy of this correction is negligible with time differences of less than 2 minutes, with 5 minutes it is always better than ± 1 ', the average measurement error of the elevation angles.

literature

• Walter Steinfatt: Astronomical Navigation , Volume II of Guide to Navigation . Transpress VEB Publishing House for Transport, Berlin 1969
• Bobby Schenk: Astronavigation . Delius Klasing Verlag, Bielefeld 2000, ISBN 3-7688-0259-0