Lesson 5: Navigation Instruments

 AGENDA: –Measurement of Depth –Measurement of Direction –Measurement of Distance –Measurement of Speed  Applicable reading: Hobbs pg Lesson 5: Navigation Instruments

Measurement of Depth  Echo Sounder (fathometer)  Hand leadline

Lead Line  Manual method of determining depth  Also allows for a sampling of the bottom type

Measurement 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

000T / 270R 090T / 000R 180T / 090R 270T / 180R

Visual Bearings can be measured in: - Degrees Relative ( # # # 0 R ) - Degrees Magnetic ( # # # pstgc OR 0 M ) - Degrees True ( # # # 0 T) The navigator must convert any of these types of bearings to True before they can be plotted on the chart. Measurement of Direction

 Azimuth or Bearing Circle  Telescopic Alidade Bearing Circle/Alidade

 Telescopic Alidade Bearing Circle

Measurement 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 Distance STADIMETER Used to determine precise ranges between ships in formation

Making an Observation with the Stadimeter  Distance is determined by: distance = height of object / tan (angle)

Parallel Ruler Plotting Instruments

Parallel Plotter Plotting Instruments

Parallel Motion Protractor Plotting Instruments

 Compass  Dividers Plotting Instruments

Nautical Slide Rule Plotting Instruments

 Given two of the following, find the third: –Speed –Distance –Time Operation of Nautical slide Rule

Measurement 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

Measurement of Speed Impeller Log

Measurement of Speed Pitometer (Pit) Log

Measurement of Speed Doppler Speed Log

 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 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 Minute Rule D = SPD 10

REVIEW  What does a fathometer measure?  What does D=Speed x 100 tell you?

QUESTIONS??