gyro and magnetic compass 1029

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 1/31

NS100 

Gyro and Magnetic Compass

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 2/31

Objectives:1. Discuss gyrocompass theory and

shipboard application.

2. Describe the differences and relationshipsof true bearings, relative bearings and ³per gyro compass´ (PGC) bearings.

3. Discuss and describe gyro error and themethods used to determine gyro error.

4. Demonstrate how to determine and correctfor gyro error.

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 3/31

Objectives:

5. Describe the purpose and operation of the magnetic compass.

6. Discuss magnetic theory and application.

7. Define, identify, and solve forvariation, deviation, compass error,magnetic bearings and true bearings.

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 4/31

Gyro Compass TheoryNorth-seeking gyroscopetwo gimbals Electronically

Stabilized

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 5/31

Gyroscope

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 6/31

Gyro Compass Theory

North-seeking Gyroscope

Gyroscopic Inertia

GravityPrecession

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 7/31

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 8/31

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 9/31

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 10/31

Gyro ApplicationsShipboard Use - two gyros placeddeep in the ship on the centerline.

Primary- (Master gyro) orientedto north/south, used for

navigation & shiphandling.

Auxiliary- (Back up gyro) oriented

east/west, used for combatsystems.

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 11/31

Gyro ApplicationsBridge - gyro repeaters are locatedon the bridge wings, navigation

table, captain¶s chair & center linewhich is referred to as ³centerline

pelorus.´ 

CIC - Command and ControlSystem.

Weapons - gyro inputs (i.e..pitch/roll), are used by fire control

com uters

Theimage cannotbed isplayed.Your computer may nothaveenough memory toopen theimage,or theimagemay havebeencorrupted.Restartyour computer,and then open thefile again.If thered x stillappears, you may haveto deletetheimageandthen insertitagain.

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 12/31

Gyro repeater 

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 13/31

Gyro Error in Navigation

Causes of Error

Friction

Ship¶s Motion

Electronic Malfunctions Power Fluctuations.

A gyro compass is an electronic/mechanicaldevice with inherent error«. the key is

knowing the error and ad justing for it

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 14/31

Gyro Error in Navigation

Determination of Error Visual Range ( The most accurate).

Ad justing Three LOP¶s (triangulation).

Used before getting underway.

Comparing a ³PGC´ bearing with a known true

bearing.

Celestial Azimuths and Amplitudes.

Comparison with a Gyro of known error.

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 15/31

A 5º westerly error

VA bears 090ºT.With reference to the Gyro compass it would bear

90º+5º=95º pgc

VAVA

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 16/31

A 5º Easterly error

VA bears 090ºT.

With reference to the Gyro compass it would bear90º-5º=85º pgc

VAVA

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 17/31

Gyro errorGyro Error - is the difference between the gyro

reading and the true bearing.

We can have a West or East Gyro error.If Gyro is Least, Error is East

If Gyro is Best, Error is West

Gyro bearing +Easterly Error =True bearing

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 18/31

Gyro error If you are on a range

bearing 089oT and the

centerline pelorus reads

090opgc,what is the gyro

error? Gyro = 090o and True =

089o,

Gyro = Best Error = West 090

o- 089

o= 1

o

Answer : 1o

Westerly Error 

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 19/31

Summary

pgc (per gyro compass)

Gyro error diff. True and Gyro norths

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 20/31

Gyro FailureIn the event of gyro failure LOP¶s are taken in

relative bearings.

The magnetic compass can be used to knowyour ship¶s head.

Rel. Bearing+Mag. Ship¶s Head=Mag. Bearing

Then the magnetic heading can be convertedto true bearing.

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 21/31

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 22/31

The variation information is contained in the compassrose closest to the ship¶s DR position

True Bearing = Magnetic Bearing + Variation(add East Variation or subtract West Variation)

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 23/31

Summary

pgc (per gyro compass)

Gyro error diff. True and Gyro northsM (magnetic)

Variationdiff. True and Magnetic norths

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 24/31

DeviationShip¶s Magnetic Field

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 25/31

DeviationDegaussing

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 26/31

Compass

Deviation table

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 27/31

Magnetic Compass ErrorDeviation + Variation = Compass Error

If observed bearing is Least, Error is East.

If observed bearing is Best, Error is West.

Example: Deviation is 2o West & Variation

is 13

o

East, what is compass error?Answer: 13o - 2o = 11o East Error

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 28/31

Applications of Compass ErrorScenario: The USS Boxer  just lost it¶s gyro

compass while steering 125o T. The conningofficer needs to give a magnetic compass

course. What course do you recommend?Given: Variation is 8o West from the compassrose on the chart, annual increase was added to

the variation.

Deviation is 2.5o

East from the ship¶scompass card for course 133o M.

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 29/31

 Applications of Compass Error 

Truly True Course

Valiant Variation

Marines Mag. Mer.

on¶t Deviation

Cry Compass

@  A

ddWeddings West

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 30/31

 Applications of Compass Error 

T = 125o T

V = 8

o

West M = 125 + 8 = 133

D = 2.5o East

C = 133 + (- 2.5)Ans = 130.5o pstgc

8/3/2019 Gyro and Magnetic Compass 1029

http://slidepdf.com/reader/full/gyro-and-magnetic-compass-1029 31/31

Summary

pgc (per gyro compass)

Gyro error 

diff. True and Gyro norths M (magnetic)

Variationdiff. True and Magnetic norths

pstgc (per steering compass)

Deviation diff. Mag and steering compass norths