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8/10/2019 controlul corectiei compasului
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The standardcompass error
determination
2014 Laurentiu - Marian Vieru
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• 1st Chapter - Introductoryconsiderations
• 2nd Chapter - Procedures ofdetermining the compass correction
• 3rd Chapter - Case study.
Structure
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I n accordance with STCW, Section A-VI I I /2 (Watchkeeping
Standards), rule 34.2 :
“The standard compass error is determined at least once per watch and, when
possible, after any major alteration of course; the standard and gyro compasses
are frequently compared, and repeaters are synchronized with the master
compass.”
Significance
8/10/2019 controlul corectiei compasului
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The standard compass error is obtained by
comparing bearings using the following relation:
Δc = B(T) – B(C)
δ = Δc – d
Δg = B(T) – B(G)
What does it mean?
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With Transit Bearings (one alignment)
∆g = Ra – Rg
Rm = Ra – d
δ = Rm – Rc
Checking the compass with coastal observations
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With equal bearing difference
Ra1 – Rc1 = ∆c'
Ra2 – Rc12 = ∆c''
Ra3 – Rc3 = ∆c'''
∆c = ( ∆c'+∆c''+∆c''')/3 ;
∆g = ( ∆g'+∆g''+∆g''')/3
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With a star at one height
With Polaris Azimuth
With the Sun/Moon at rise and set
Checking the compass with astronomical
observations
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Conclusions
• The standard compass error determination, represent the day by day activity for
an officer of the watch, in calculating Δc .
• The standard error for gyro compass, Δ g is calculated at grater periods of time,when is possible to apply more precise procedures; usually the gyrocompass is checked
by comparing it’s indications whit those of the magnetic compass.
• For having a very small lateral alidade lean error, it is necessary that the star
we choose to have a small altitude.
• It is recommended to execute simultaneously the standard error determination
for both magnetic and gyro compasses.
• To avoid errors caused by the time necessary to physically move the Alidade
from the gyro repeater onto the magnetic compass,the next procedure is recommended:
One observer reads gyro bearing and relative bearing simultaneously.
In the same time, another observer reads the compass heading of the ship.
∆g is calculated:
∆g = Ra – Rg , Az can be Ra; ∆c is calculated:
Rcd = Rci + 180º
Rc = Rp + Dc
∆c = Ra – Rc
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The standard compass
error determination
Thank you !