05 navigation instruments
DESCRIPTION
fdTRANSCRIPT
AGENDA:– Measurement of Depth– Measurement of Direction– Measurement of Distance– Measurement of Speed
Applicable reading: Hobbs pg. 110-128.
Lesson 5: Navigation InstrumentsLesson 5: Navigation Instruments
Measurement of DirectionMeasurement of Direction
Bearing: the horizontal direction of one terrestrial point as measured from another, expressed as an angle from 0 to 360 degrees.
There are three references for bearings:– Relative– Magnetic– True
Visual Bearings can be measured in:
- Degrees Relative ( # # # 0R )
- Degrees Magnetic ( # # # pstgc OR 0M )
- Degrees True ( # # # 0T)
The navigator must convert any of these types of bearings to True before they can be plotted on the chart.
Measurement of DirectionMeasurement of Direction
Measurement of DistanceMeasurement of Distance
Radar - Distance is obtained by a radio wave that is transmitted into the air and returns as an echo. The time interval between transmission and return can be converted into a physical range.
Used for distance (range) only!!Not normally used for bearings
Measurement of DistanceMeasurement of Distance
STADIMETERUsed to determine precise ranges between ships in formation
Making an Observation with the Making an Observation with the StadimeterStadimeter
Distance is determined by: distance = height of object / tan (angle)
Given two of the following, find the third:– Speed
– Distance
– Time
Operation of Nautical slide RuleOperation of Nautical slide Rule
Measurement of SpeedMeasurement of Speed
Speed over Ground (SOG) = true speed Speed through the water
SPEED OVER GROUND• Direct output of many
electronic navigation systems (GPS, Loran)
SPEED THROUGH WATER• Impeller Log• Pitotmeter Log• Doppler Speed Log• Shaft RPM
The Distance in yards that a ship travels in 3 minutes (D) is equal to the Ship’s Speed (Spd) in knots multiplied by 100.
D = Spd x 100
3 Minute Rule3 Minute Rule
The Distance in nautical miles that a ship travels in 6 minutes (D) is equal to the Ship’s Speed (Spd) in knots divided by 10.
6 Minute Rule6 Minute Rule
D = SPD
10