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1. 1. NEXT GYROCOMPASS CALIBRATION AND DGPS INTEGRITY CHECK AP220 –SUG571 OCEANOGRAPHY & OFFSHORE SURVEYINGMOHD NOR BASYAR BIN SAAD 2009736911BANTIN ANAK IBIK 2009339845MOHAMAD KHAIRI BIN MOHD GHAZALI 2009668914 START MARA TECHNOLOGY UNIVERSITY, UiTM SHAH ALAM, MALAYSIA
2. 2. Calibration of NEXTGyrocompass and DGPS
3. 3. NEXT`
4. 4. Gyrocompass Field Calibration NEXT 1. On Gyrocompass 2. Record gyro reading ,O 3. For example, vessel heading =270⁰ 4. Vessel heading = gyro reading = O Note: Bearing of vessel heading given270⁰00’00” by gyro compass. Baseline along vessel heading
5. 5. NEXT Gyrocompass Field Calibration270⁰00’00” Jetty/Wharf = Known point Land
6. 6. 1st Method (1 stObservation) NEXTTransfer bearing or distance from known point at Jetty/Wharf(Stn1 and Stn2) to the vessel baseline along vessel heading Calculate of vessel baseline, C. Vessel baseline, 3 – 4 = 280⁰ = C Gyrocompass reading = 270⁰ = O Gyro calibration = C – O = 280⁰ - 270⁰ = 10⁰ Then apply +10⁰ to gyrocompass Stn3 Stn4 Baseline (b/d) Ocean b/d b/d b/d = Known point Stn1 Stn2 Jetty/wharf
7. 7. NEXT1st Method (2nd Observation)Checking Calculate of vessel baseline, C. Vessel baseline, 3 – 4 = 280⁰ = C Gyrocompass reading = 270⁰ = O Gyro calibration = C – O = 280⁰ - 270⁰ = 10⁰ Then apply +10⁰ to gyrocompass Stn3 Stn4 Baseline (b/d) Ocean b/d b/d b/d = Known point Stn1 Stn2 Jetty/wharf
8. 8. NEXT2nd MethodComparison of Azimuth Bearing with vessel heading Stn1 Baseline Stn2 •Azimuth Bearing 1 – 2 = 280⁰ = C •Gyrocompass reading = 270⁰ •Gyro Calibration = C – O = +10⁰Sun •Apply +10⁰ to gyrocompass
9. 9. 3rd Method NEXTDGPS method •DGPS reading 1(x,y) & 2(x,y) •Calculate 1 – 2 = 280⁰ = C •Gyrocompass reading/ baseline = 270⁰ = O •Gyro calibration = C – O = +10⁰ •Apply +10 ⁰ to gyro compass Baseline (b/d)? R1 R2 Ocean Jetty/wharf
10. 10. DGPS Integrity Check NEXT•Before Starting the Job..•Software setting ex. Transformation Parameter forHydroPro must be set/checked.. •Check list GEODETIC PARAMETERS Projection Grid :(MRSO) Spheroid :Everest Modified Semi Major Axis :6377304.06m Semi Minor Axis :6356103.04m Flattening :1/300.8017 Scale Factor :0.99984 Skew (Gamma) :323º 07’ 48.36’’ False Easting :804671.30m False Northing :0.00m Latitude of Origin :4º 00’ 00’’N Longitude of Origin :102º 15’ 00’’E
11. 11. NEXT DGPS Integrity Check Survey boat is along side the jetty. The GPS antenna is closed to the a known point. The coordinates of known point R1 and the GPS antenna are then compared to check against any Stn1 Jetty gross error. Note: Compare ( R1 – Stn1) < ±2m = Known pointLand
12. 12. DGPS Integrity Check NEXT Transit Method Motion: 1. Go around platform in clockwise direction for set 1. Radius 400m 2. Second set go around in Platform counter clockwise Leg direction. 3. Go around a known coordinated platform about 400m.vessel Base/check point on platform/rig
13. 13. DGPS Integrity Check NEXT Transit Method Operation: Fix8 Fix1 1. The surveyor onboard survey vessel stands right under the GPS antenna. 2. Use the binocular observe corner legs of the platform until theFix7 nearest and the farthest legs(on Fix2 the same edge of the platform) become coincided. 3. Fix is made and the position of the GPS antenna is recorded. 4. 8 fixes altogether for each set of Fix3 observation.Fix6 5. Platform center is determined by calculating the observed reading. 6. The result of transit is then compared with the actual platform center coordinates, acting as Fix4 quality control for the positioning Fix5 system onboard.
14. 14. DGPS Integrity Check NEXT Transit Method Fix8 Fix1 Note: • Any gross error caused by transformation parameters can be identified.Fix7 • If the comparison result show Fix2 that the observed platform center coordinate is beyond the survey tolerance ±2m. Fix3Fix6 Fix5 Fix4
15. 15. NEXTTHANK YOU