New Advances
Flux Gate Magnetic Compass
Ring Laser Gyrocompasss
GPS Compass & DGPS Compass

Flux Gate Compass
Two harmonic coils wrapped around a magnetic core.
Earth’s magnetic field changes the core’s magnetic induction.
The coils sense the changes.
Electronics calculate the magnetic field necessary to cause the change.

Flux Gate Compass

Flux Gate Compass
To minimize deviation, the sensor is placed at the top of the mast.
Residual deviation is automatically calculated as the ship changes course 360°.
It makes its own deviation table!
Deviation is automatically applied.

Flux Gate Compass
Operator can input the variation.
Resulting true direction is sent to digital equipment.

Ring Laser Gyrocompass
Two laser beams travel in opposite directions around a fiber-optic ring.
When the compass (the ship) isn’t turning, the beams are in phase.
When the compass turns, the beams are out of phase.
The quicker the turn, the larger the phase differences.

Ring Laser Gyrocompass

GPS Compass

Piloting Instruments
Tools to measure:
Direction
Distance
Speed
Depth

Direction
Bearing Circle
Placed on top of gyro repeater or magnetic compass.
Peep vane and far vane
(wire) are lined up with object of interest.
Compass card is reflected by mirror.

Direction
Azimuth Circle
A bearing circle with attachments for celestial observations.
Azimuth = bearing of a celestial object.

Direction
Telescopic Alidade
A bearing circle with a telescope attached.
Object is magnified, enabling greater precision, especially at long range.

Direction
Pelorus
A “dumb compass”
A rotating compass card on a fixed stand.
Set to ship’s heading then bearing is taken.
Heading set to 0 = relative bearings
Actual heading set = true bearings

Direction
Hand Bearing
Compass
Handheld magnetic compass.
Used on small vessels.
Configured for ease of taking bearings.

Taking a bearing
Direction

Distance
Radar
A radio wave is transmitted and returns as an echo. Time interval between transmission and return is converted into a physical range.

Distance
Stadimeter

Distance
Measures angles between objects.
If separation or height is known, distance can be calculated.

Distance
Distance = height of object / tan (angle)

Speed
Can measure:
Speed Over Ground (SOG)
Speed relative to the fixed earth.
Speed Through Water
Relative to water around the vessel.

Speed
Chip Log
Wood attached to a knotted line.
Thrown behind the vessel
Knots counted for a set time period.
Speed through the water

Speed
Pitot-static Log
Retractable “Pit Sword” hangs below vessel.
Measures speed by pressure differential.
Greater pressure = greater speed

Speed
Impeller Log
A propeller-type device hangs below the vessel on a rod.
Water flow over propeller causes it to spin.
Faster spin = faster speed.

Speed
Electromagnetic Log
Water conducts electricity.
Measures induced voltage.
Greater voltage = greater water flow.

Speed
Doppler Speed Log
Measures frequency shift of reflected sound waves.
SOG or Speed Through Water

Speed
Taffrail Log

Depth
Echo Sounder (Fathometer)
Sound is transmitted and reflected from the bottom.

Depth
Depth = speed x ½ time interval
Speed is set at 4800 ft/sec.
But, it varies with salinity, temperature, pressure.

Depth
Can display depth in feet, fathoms or meters.
Check the setting!

Depth

Piloting Instruments
Dividers/Compass

Piloting Instruments
Triangles

Piloting Instruments
Parallel Rulers

Piloting Instruments
Parallel Plotter

Piloting Instruments
Three Arm Protractor

Piloting Instruments
Nautical Slide Rule

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