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CHARTWORK ANDFIXING
Gruntproductions 2009
A Brief by Lance Grindley
Gruntproductions 2009
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.
Gruntproductions 2009
CHARTWORK CONVENTIONS
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
Gruntproductions 2009
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
Gruntproductions 2009
Gruntproductions 2009
CHARTWORK CONVENTIONS
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)
Gruntproductions 2009
Gruntproductions 2009
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
Gruntproductions 2009
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.
Gruntproductions 2009
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 !!!!
Gruntproductions 2009
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.
Gruntproductions 2009
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
Gruntproductions 2009
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.
Gruntproductions 2009
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
Gruntproductions 2009
Chord of a CircleChord of a Circle
Gruntproductions 2009
HSA FIXHSA FIX
09000900
Gruntproductions 2009
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°
Gruntproductions 2009
Gruntproductions 2009
Douglas protractor
Gruntproductions 2009
FIXING BY RELATIVE ANGLESFIXING BY RELATIVE ANGLES
Cou
rse
030°
G15
G45
G8035
30
Gruntproductions 2009
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
Gruntproductions 2009
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.
Gruntproductions 2009
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.
Gruntproductions 2009
Running Fix Running Fix
4545 09000900
09000900
0900
Gruntproductions 2009
Gruntproductions 2009
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.
Gruntproductions 2009
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.
Gruntproductions 2009
Calculating VSA (1)Calculating VSA (1)
MHWSMHWS
ElevationElevation
Gruntproductions 2009
Gruntproductions 2009
Calculating VSA (2)Calculating VSA (2)
MHWSMHWS
ElevationElevation
Chart DatumChart Datum
Sea LevelSea Level
Height of TideHeight of Tide
Gruntproductions 2009
Gruntproductions 2009
Calculating VSA (3)Calculating VSA (3)
MHWSMHWS
ElevationElevation
Chart DatumChart Datum
Sea LevelSea Level
Height of TideHeight of Tide
Gruntproductions 2009
Gruntproductions 2009
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
Gruntproductions 2009
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?
Gruntproductions 2009
Gruntproductions 2009
SHOOTING UPSHOOTING UP
Bn
FSA) By bearings A) By bearings from fixesfrom fixes
1000
1015
1030
190
8
Gruntproductions 2009
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
Gruntproductions 2009
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
Gruntproductions 2009
The DR PositionThe DR Position
Course Steered and Speed Course Steered and Speed through the waterthrough the water
FixFix
0900
30
Gruntproductions 2009
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
Gruntproductions 2009
FixFix
Course RequiredCourse Required
Tidal Tidal Stream Stream VectorVector
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 SteerCourse to Steer
Gruntproductions 2009
Tidal Tidal Stream Stream VectorVector
Course to Steer (3)Course to Steer (3)
Course to SteerCourse to Steer
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
Gruntproductions 2009
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
Course and Speed Made Good
Gruntproductions 2009
EP Based on FixesEP Based on Fixes
14151415
Course Steered and Speed Course Steered and Speed through the waterthrough the water 2727
14271427
Course and Speed Made Good
Course and Speed Made Good
3131
Gruntproductions 2009
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
Gruntproductions 2009
Any Any QuestionsQuestions
??