GYROCOMPASS CALIBRATION AND

DGPS INTEGRITY CHECK

AP220 –SUG571 OCEANOGRAPHY & OFFSHORE SURVEYING

MARA TECHNOLOGY UNIVERSITY, UiTM SHAH ALAM, MALAYSIA

MOHD NOR BASYAR BIN SAAD 2009736911BANTIN ANAK IBIK 2009339845MOHAMAD KHAIRI BIN MOHD GHAZALI 2009668914

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START

Calibration of Gyrocompass and DGPS

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Gyrocompass Field Calibration

1. On Gyrocompass2. Record gyro reading ,O3. For example, vessel

heading =270⁰4. Vessel heading = gyro

reading = O Note: Bearing of vessel heading given by gyro compass.

Baseline along vessel heading

270⁰00’00”

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Gyrocompass Field Calibration

270⁰00’00”

Land

Jetty/Wharf

= Known point

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1st Method (1st Observation)Transfer bearing or distance from known point at Jetty/Wharf(Stn1 and Stn2) to the vessel baseline along vessel heading

Baseline (b/d)

Stn1

b/d

Stn2

b/d b/d

Ocean

Stn4Stn3

= Known point

Jetty/wharf

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Calculate of vessel baseline, C.Vessel baseline, 3 – 4 = 280⁰ = CGyrocompass reading = 270⁰ = O

Gyro calibration = C – O = 280⁰ - 270⁰ = 10⁰Then apply +10⁰ to gyrocompass

Baseline (b/d)

Stn1

b/d

Stn2

b/d b/d

Ocean

Stn4Stn3

= Known point

Jetty/wharf

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1st Method (2nd Observation)

Checking Calculate of vessel baseline, C.Vessel baseline, 3 – 4 = 280⁰ = CGyrocompass reading = 270⁰ = O

Gyro calibration = C – O = 280⁰ - 270⁰ = 10⁰Then apply +10⁰ to gyrocompass

2nd MethodComparison of Azimuth Bearing with vessel heading

•Azimuth Bearing 1 – 2 = 280⁰ = C•Gyrocompass reading = 270⁰•Gyro Calibration = C – O = +10⁰•Apply +10⁰ to gyrocompassSun

BaselineStn1 Stn2

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3rd MethodDGPS 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

Jetty/wharf

OceanBaseline (b/d)?

R1 R2

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DGPS Integrity Check

•Before Starting the Job..•Software setting ex. Transformation Parameter for HydroPro must be set/checked..

GEODETIC PARAMETERS Projection Grid :(MRSO)Spheroid :Everest ModifiedSemi Major Axis :6377304.06mSemi Minor Axis :6356103.04mFlattening :1/300.8017Scale Factor :0.99984Skew (Gamma) :323º 07’ 48.36’’False Easting :804671.30mFalse Northing :0.00mLatitude of Origin :4º 00’ 00’’NLongitude of Origin :102º 15’ 00’’E

•Check list

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DGPS Integrity Check

Land

Jetty

= Known point

Survey boat is along side the jetty.The GPS antenna is closed to the a known point.The coordinates of known point and the GPS antenna are then compared to check against any gross error. Note: Compare ( R1 – Stn1) < ±2m

R1

Stn1

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DGPS Integrity Check Transit Method

Radius 400m

Motion:1. Go around platform in

clockwise direction for set 1.

2. Second set go around in counter clockwise direction.

3. Go around a known coordinated platform about 400m.

Base/check point on platform/rig

vessel

Platform Leg

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Operation:1. The surveyor onboard survey vessel

stands right under the GPS antenna.2. Use the binocular observe corner

legs of the platform until the nearest and the farthest legs(on 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 observation.

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 quality control for the positioning system onboard.

Fix1

Fix2

Fix3

Fix4Fix5

Fix6

Fix7

Fix8

DGPS Integrity Check Transit Method

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Note:• Any gross error caused by

transformation parameters can be identified.

• If the comparison result show that the observed platform center coordinate is beyond the survey tolerance ±2m.

Fix1

Fix2

Fix3

Fix4Fix5

Fix6

Fix7

Fix8

DGPS Integrity Check Transit Method

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THANK YOU

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