Transcript Lesson 19 - Navigational Equipment

Navigation
NAU 102
Lesson 19
GPS Compass
Piloting Instruments
Tools to measure:
Direction
Distance
Speed
Depth
Direction
Bearing Circle
Placed on top of gyro
repeater or magnetic
compass.
Used to measure bearings of
terrestrial objects.
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.
Direction
Taking a
bearing
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
Similar to a
sextant, but
without the
shade glass.
Distance
Stadimeter
Measures angles between objects.
If separation or height is known, distance can
be calculated.
Distance
Distance = height of object / tan (angle)
Distance
The air draft of a vessel is 130 feet. The angle
between the top of the mast and the waterline is
8.5° as measured by stadimeter. What is your
distance from the ship?
Distance = height of object / tan (angle)
Distance = 130 ft / tan (8.5°)
Distance = 869.9 ft
Speed
We can measure:
Speed Over Ground (SOG)
Speed relative to the fixed earth.
Speed Through Water
Relative to the 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
Introduction to Navigation
Questions?