How to get compass error by sun
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The document provides a detailed procedure for calculating ship navigation parameters, including GMT conversion, geographical and magnetic data needed for accurate navigation. It outlines specific steps to derive true bearing and account for declination, variations, and errors. This navigation guide emphasizes the importance of accurate data input for determining the precise course and bearings of a vessel.
How to get compass error by sun
- 1. By: Gian Gabriel Ibo Deck Cadet
- 2. First you need the following information -Date -Time in UTC or GMT - Ships Posotion -Variation (can be found on charts and ECDIS) -Gyro course -Gyro Bearing -Magnetic Course
- 3. Date: 22 July 1997 Time: 15h 10m 20s (Philippine Local Time) Position: Latitude- 12° 00’N Longitude- 121° 30’ E Variation: 1.25’W Gyro Course: 270° Gyro Bearing: 286.1° Magnetic Course: 265°
- 4. 1.) First is to get the GMT 15h 10m 20s- Local Time (+8 time zone) 08h 00m 00s(-) 07h 10m 20s - GMT
- 5. - Get the GHA by the use of the Nautical Almanac - Get also the increments by the use of the Nautical Amanac
- 8. You Have now your GHA and Increments GHA= 283° 23.9’ INC= 2° 35.0’ + Always plus GHA= 285° 58.9’ Long= 121° 58.9’E LHA= 406° 88.9’ E +1 -60 407° 28.9’ -360° LHA= 47° 28.9’ W E (+) W (-) -360 if LHA is over 360°
- 10. Get Declination Dec= 20° 15.1’ N 0.1’ (-) Dec= 20° 15.0’ N d= 0.5 (bottom part of the declination page) Minus because Declination Is Decreasing
- 11. Get the True Bearing Tan Z= Sin LHA Tan Dec x Cos lat (+)(-) Cos LHA x sin Lat (+) Different name (-) Same name Lat and Dec
- 12. tanZ= Sin (47° 28.9) Tan(20°15.0’)xcos(12°) – cos (47°28.9’)x sin(12°) tanZ= (3.34) Z= tan-1(3.34) Z= N 73.36 W N S EW -360 As is +180 -180 360 Zn= 286.4° LHA Declination
- 13. OR YOU CAN SOLVE IT BY USING THE ABC METHOD
- 14. A= Tan Lat Tan LHA B= Tan Dec Sin LHA C= A(+,-)B Change name of latitude if LHA is not in range between 90°-270° Name of Declination Z= Cx Cos lat= x 1/x= tan-1= Z
- 15. A= Tan 12° Tan 47°28.9’ B= Tan 20°15 Sin LHA C= A(+,-)B Z= Cx Cos lat= x 1/x= tan-1= Z =0.19S =0.50N =0.31N 0.31 x cos(12°)= 0.30 1/0.30= 3.33 Tan-1(3.33)= N73.36W TB=286.4°
- 16. GB= 286.1° TB= 286.4°(-) GE= 0.3 E GC=270° TC= 270.3° MC=265° CE= 5.3E Var= 1.4W (E) Dev= 6.7 E Remember the rule Compass best Error (W) Compass Least Error (E) Change the name of the Variation when solving for The deviation
- 17. Checking: C- 265° D- 6.7°E M- 271.7° V- 1.4°W T- 270.3°
- 18. Thank you and Godbless