Coastal navigation lrg

CHARTWORK ANDFIXING

Gruntproductions 2009

A Brief by Lance Grindley


CHARTWORK CONVENTIONS

140 (142)

0800

06

12

1.2B

060900

06

Force 5

Planned TrackPlanned Track (To be made good): (To be made good):A bold thick line.A bold thick line.

CourseCourse: Along the track.: Along the track.

Course to SteerCourse to Steer: In brackets.: In brackets.

SpeedSpeed: Vertically in a box.: Vertically in a box.

DR (Dead Reckoning)DR (Dead Reckoning): Allowing for direction steered: Allowing for direction steeredat speed through the water only and for NO OTHER factors.at speed through the water only and for NO OTHER factors.

Tidal StreamTidal Stream: Three arrow heads from a tidal diamond,: Three arrow heads from a tidal diamond,show rate and effective time.show rate and effective time.

WindWind::

EP (Estimated Position)EP (Estimated Position): Estimated from course steered through water, : Estimated from course steered through water, allowing for wind, tidal stream, current etc.allowing for wind, tidal stream, current etc.



Distance to DestinationDistance to DestinationShown in milesShown in miles..

Expected time in a positionExpected time in a position

Darkness Darkness Across the trackAcross the track

Raising and Lowering of LightsRaising and Lowering of Lights

Change of ChartChange of Chart

1810 SS

Wolf Rock Lt

0547SR

Chart 2052

230

0800


POSITION LINES

Visual bearing from an objectVisual bearing from an object

Visual bearing transferredVisual bearing transferred

Radar range/VSARadar range/VSA

Radio Fixing AidRadio Fixing Aid

Astronomical position lineAstronomical position line SUN 0932

0900

Position line by transit

Ship

f




Potential Dangers Potential Dangers - near track should - near track should be highlightedbe highlighted

Safe Depth Safe Depth - hatch in - hatch in LDL for ship and HOTLDL for ship and HOT

Clearing Bearings Clearing Bearings - Solid arrow - Solid arrow heads towards object, NMT or NLTheads towards object, NMT or NLT

Wheel over bearings (2) Wheel over bearings (2) - show - show position and est time with openposition and est time with openarrow head, show wheel if not arrow head, show wheel if not standardstandard

195

(196

)

181(

182)

105(104)

NMT 200

NM

T 176

NMT 160

140

090

POSITION LINES LEADING TO POSITION LINES LEADING TO FIXESFIXES

►Compass or Gyro bearing (3 or more)Compass or Gyro bearing (3 or more)►Transit (must be sensitive)Transit (must be sensitive)►Relative bearingRelative bearing►Horizontal Sextant AngleHorizontal Sextant Angle►Vertical Sextant AngleVertical Sextant Angle►Range by optical instrumentsRange by optical instruments►Range by raising/lowering of lights Range by raising/lowering of lights

(Horizon range)(Horizon range)



POSITION LINES LEADING TO FIXESPOSITION LINES LEADING TO FIXES

►SoundingsSoundings►Astronomical position lineAstronomical position line►Radar rangeRadar range►D/F bearing D/F bearing ►Radio fixing aidsRadio fixing aids


USING CHARTSUSING CHARTS

►Always use the largest scale chart Always use the largest scale chart appropriate to the purpose:appropriate to the purpose: Corrected first.Corrected first. More detail.More detail.

►Use nearest compass rose:Use nearest compass rose: Correct Variation.Correct Variation. Less projection distortion.Less projection distortion. Parallel ruler has less distance to travel.Parallel ruler has less distance to travel.


USING CHARTSUSING CHARTS

►Transfer position by range and bearing and Transfer position by range and bearing and Lat and Long.Lat and Long.

►Check unit of depth.Check unit of depth.►Measure distance opposite latitude - Measure distance opposite latitude -

Mercator.Mercator.►Only one chart on the table at any one time.Only one chart on the table at any one time.►Use soft pencil - Don’t dig.Use soft pencil - Don’t dig.►Don’t doodle !!!!Don’t doodle !!!!


CHANGING CHARTSCHANGING CHARTS

►Transferred positions may be fix, DR or EP.Transferred positions may be fix, DR or EP.►Transfer position by range and bearing and Transfer position by range and bearing and

Lat and Long.Lat and Long.►Note down position in Nav Record Book.Note down position in Nav Record Book.►Plot onto new chart.Plot onto new chart.►Fix to verify position as soon as practicable.Fix to verify position as soon as practicable.


The FixThe Fix

0926

Visual FixVisual Fix : :

-made up of transits, -made up of transits, gyro bearings or gyro bearings or compass bearingscompass bearings

Radar FixRadar Fix: :

-made up of at -made up of at least three least three radar rangesradar ranges

0957


FIXINGFIXING

►Cross cut of 2 position lines. 3 Cross cut of 2 position lines. 3 position lines are used as error check.position lines are used as error check.

►Use Visual / radar conspicuous points.Use Visual / radar conspicuous points.►Are points charted ?Are points charted ?►Avoid blind arcs (visual and radar).Avoid blind arcs (visual and radar).►Aim for a good angle of cut.Aim for a good angle of cut.►Aim to fix at least every 6 minutes.Aim to fix at least every 6 minutes.


Horizontal Sextant AnglesHorizontal Sextant Angles►AdvantagesAdvantages►Potentially the most accurate method of Potentially the most accurate method of

fixing.fixing.►Freedom from Gyro repeats.Freedom from Gyro repeats.►Can be used in event of Gyro failureCan be used in event of Gyro failure..►DisadvantagesDisadvantages ►Takes longer to obtain the fix.Takes longer to obtain the fix.►Manpower intensive.Manpower intensive.►Requires three suitable fixing pointsRequires three suitable fixing points


Chord of a CircleChord of a Circle


HSA FIXHSA FIX

09000900


HSA FIX HSA FIX

►Plotted using:Plotted using: HSA Lattice chart.HSA Lattice chart. Douglas Protractor.Douglas Protractor. Station Pointer.Station Pointer.

►Beware of circular fixesBeware of circular fixes..

When not to fix by HSA or bearingsWhen not to fix by HSA or bearings

PossiblePositions

q°

q°

q°

f°

f°

f°



Douglas protractor


FIXING BY RELATIVE ANGLESFIXING BY RELATIVE ANGLES

Cou

rse

030°

G15

G45

G8035

30


VISUAL FIXVISUAL FIX

Duration of fixDuration of fix

Ship Movement:Delay between first and last bearing been taken.Approx 10-15 Secs = 30 – 100m at 12 Kts


Sources of the Cocked HatSources of the Cocked Hat►Reading Error:Reading Error:

+/- 1/2 +/- 1/2 approx 50 Meters at 3nmapprox 50 Meters at 3nm

►Compass Error:Compass Error: Gyro Compass accurate to +/- 1.Gyro Compass accurate to +/- 1. 0.3 = 33 meters at 3nm.0.3 = 33 meters at 3nm.


Detection of Gyro ErrorDetection of Gyro Error

►Transits.Transits.►Bearing of celestial body.Bearing of celestial body.►Line of Jetty.Line of Jetty.►Comparison of observed / charted Comparison of observed / charted

bearing from a known position.bearing from a known position.►Reduction of a cocked hat using Reduction of a cocked hat using

Station Pointer.Station Pointer.


Running Fix Running Fix

4545 09000900

09000900

0900



Range by Vertical AngleRange by Vertical Angle

►Angle measured by sextant.Angle measured by sextant.►Elevation of charted objects Elevation of charted objects

given above the Datum of MHWS.given above the Datum of MHWS.►Value of MHWS either given or Value of MHWS either given or

obtained from Tidal Level Table obtained from Tidal Level Table on chart.on chart.

►Height of tide usually given.Height of tide usually given.►Beware of index error if given.Beware of index error if given.


Nories TablesNories Tables

►Distance by Vertical Angle (page Distance by Vertical Angle (page 478)478)

►Calculator can be used if Calculator can be used if desired.desired.

►Tan VSA = h/d where h is height Tan VSA = h/d where h is height of object and d is distance from of object and d is distance from object.object.


Calculating VSA (1)Calculating VSA (1)

MHWSMHWS

ElevationElevation




MHWSMHWS

ElevationElevation

Chart DatumChart Datum

Sea LevelSea Level

Height of TideHeight of Tide



Fixing by a bearing and a soundingFixing by a bearing and a sounding

M97/1295-9-13

Fixing Fixing ProcedureProcedure

► Select objects (consult chart) Select objects (consult chart) ► Write down in notebookWrite down in notebook► ““Shoot up” objects - think aheadShoot up” objects - think ahead► Take 3 bearings and shoot up a further markTake 3 bearings and shoot up a further mark► Time fix to coincide with DR/EPTime fix to coincide with DR/EP► Take bearings quickly (remember last 2 digits)Take bearings quickly (remember last 2 digits)► Bow/Quarter first, beam lastBow/Quarter first, beam last► Note timeNote time► PlotPlot


Selection of Selection of MarksMarks

►Good cutGood cut►Near objects to reduce errorsNear objects to reduce errors►Charted and visible!Charted and visible!►All visible from same repeaterAll visible from same repeater►Are they circular?Are they circular?



SHOOTING UPSHOOTING UP

Bn

FSA) By bearings A) By bearings from fixesfrom fixes

1000

1015

1030

190

8


SHOOTING UPSHOOTING UP

Bn

FS 1000

Hotel Conspic

B) By transitsB) By transits

A

B

A. Buoy O Hotel 117A. Buoy O Hotel 117

B. Buoy O Church 088B. Buoy O Church 088

190

8


OPENING BEARINGOPENING BEARING

Stab Pt

All Saints

All

Sain

ts o

pens

018

W/O

First church will openFirst church will open

All saints will appear All saints will appear when Stab Pt bears 018when Stab Pt bears 018


The DR PositionThe DR Position

Course Steered and Speed Course Steered and Speed through the waterthrough the water

FixFix

0900

30


The EP PositionThe EP Position

FixFix

Course Steered and Speed Course Steered and Speed through the waterthrough the water

Course and Speed Made GoodCourse and Speed Made Good

Tidal Tidal Stream Stream VectorVector

FixFix

0900

30

30


FixFix

Course RequiredCourse Required


Course to SteerCourse to Steer

Radius Vector for Radius Vector for Speed through the Speed through the waterwater

Speed Made GoodSpeed Made Good




Course to Steer (3)Course to Steer (3)


Speed Made GoodSpeed Made Good

This is a vector (relative velocity) This is a vector (relative velocity) triangle which can be constructed triangle which can be constructed in any convenient position such as in any convenient position such as the Compass Rosethe Compass Rose


Assessing the Tidal Assessing the Tidal StreamStream

14151415

Course Steered and Speed Course Steered and Speed through the waterthrough the water 2727

14271427

Course and Speed Made Good



EP Based on FixesEP Based on Fixes

14151415

Course Steered and Speed Course Steered and Speed through the waterthrough the water 2727

14271427



3131


To reach a required To reach a required positionposition

14101410 A AA A

15001500

1515

Direction (Course) and Distance to Direction (Course) and Distance to be steamed in the next 45 minutes be steamed in the next 45 minutes


Any Any QuestionsQuestions

??

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