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OOW 3000 > CHARTWORK > Flashcards

CHARTWORK Flashcards

1
Q

Correcting Charts

A
  • Current Cumulative List. Check latest edition date against date of chart.
  • Check for corrections that apply to the chart, listed in the Cumulative List.
  • Check Weekly NtoMs published since the Cumulative List for subsequent corrections and new editions.
  • Look at bottom left hand corner of the chart and see which corrections have or have not been applied to the chart.
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2
Q

Correcting Publications

A

Annual Summary of NtoMs - Part 2.
-latest edition + updates applied?
then check any subsequent Weekly NtoMs.
Check and Record amendments in front of book.

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3
Q

Explain a DR
+ How is it shown on a chart?

A

Calculated rough position derived from the Vessel’s course and STW.

Shown on the chart with a small cross and time.

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4
Q

Explain an EP

A

Most accurate position calculated using:
leeway,
current and or tide.

Shown on the chart as a triangle with time.

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5
Q

Explain a Running Fix
(6)

A
  1. Visual brg of charted object (note time and speed)
  2. Convert to True brg using compass error for the ships head.
  3. Run for a fixed amount of time + take 2nd brg of the same object and plot on chart.
  4. Using any start point on the 1st brg line and lay ships heading including leeway for the time period measured. Then add in the tidal vector to find an EP.
  5. The final stage is to transfer the first position line across to run thorough the EP and extend it till it crosses the second position line.
  6. The resultant position is a fix.
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6
Q

Geographical Range

A

MAX distance a light can be seen.
Determined by:
-height of eye
-height of structure
-curvature of the Earth

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7
Q

Luminous Range

A

MAX distance a light can be seen.
Determined ONLY by:
- intensity of the light
- visibility at the time.
NO account of elevation, observer’s height of eye, or curvature of Earth.

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8
Q

Nominal Range

+ where can you find this info?

A

Luminous range @ meteorological visibility of 10 miles.
Details of these ranges - Admiralty List of Lights.

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9
Q

Chart Features

A

NP5011, used to be called Chart 5011.
Learn for Paper Charts and ECDIS.

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10
Q

Explain Tidal Diamonds

Set and rate?

A
  • SET. Direction that a given current or tidal stream is moving. (degrees)
  • RATE. Velocity of the current or tidal stream (knots)
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11
Q

Explain primary ports use of ATT

A

The Admiralty Tide Tables
Part I: tidal predictions for Standard Ports. These are the tabulated predictions for the time and height of High and Low Water at the specific port.
Part II: time and height differences for predicting the tide at Secondary Ports.

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12
Q

Types of Chart Projections

A

Mercator
Transverse Mercator
Gnomonic

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13
Q

Mercator
(6)

A
  1. Rhumb Lines - straight lines.
  2. Great Circles - curved.
  3. Used for normal Nav.
  4. Appropriate Lat scale for measuring.
  5. Land distorted N and S.
  6. Parallels of long equally spaced.
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14
Q

Transverse Mercator
(6)

A
  1. Used for large scale charts.
  2. Mercator turned through 90 deg.
  3. Parallels of Lat now equally spaced.
  4. Parallels of long NOT equally spaced.
  5. Land distorted E and W.
  6. Distance measured as normal
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15
Q

Gnomonic
(5)

A
  1. Used for Ocean Navigation PLANNING
  2. Parallels of lat are curved
  3. Parallels of long converge at poles.
  4. Great Circles - straight
  5. Rhumb lines - curved
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16
Q

Great Circle

A

Great Circle:
Used for long ocean passages
Shortest distance between any 2 points on the Earth’s Sphere.

17
Q

Composite Track

A

Used when a great circle goes into unnecessarily high latitudes or passes over land.
Follows the course due East or West along the limiting latitude between the two great circle routes.

18
Q

Variation

What is it?

What is it affected by?

Where is the information shown?

A

TVMDC

The angular difference between True North and Magnetic North.
Measured in degrees
Named E / W of True North.

Dependent on EARTHS MAGNETIC FIELD

Isogonal Chart / Compass Rose

19
Q

Deviation

What is it?

What is it affected by?

A

TVMDC

The angular difference between Magnetic North and Compass North.
Measured in degrees
Named E / W of Magnetic North.

Dependent on SHIPS HEADIING

20
Q

Rhumb Lines

A

A line which cuts all meridians at the same angle.

21
Q

Explain

-Tides + its cause
-Tidal Streams
-HoT

Information sources?

A

Gravitational pull of the Sun and moon.

Tides are the periodic vertical movements of the water on the Earth’s surface.
Tidal streams are the periodic movements of the water that result from the tides.

Height of Tide: vertical distance between the water level and chart datum.

ADMIRALTY Tide Tables and Tidal Stream Atlas. (ATT)

22
Q

What is a Sextant and its uses?
(3)

A

Tool to measure the angle between two objects.

  • Vertical Sextant Angles
  • Horizontal Sextant Angles
  • Ocean Navigation
23
Q

GOCC

Fixed Errors (SEXTANT)
(4)

A

Depends on the quality of the sextant:

-Graduation Error
Graduations on the arc / micrometer / screw thread are not cut accurately.

-Collimation Error
Telescope not parallel with plane of the instrument.

-Centring Error
Pivot of the Index Bar is not at the centre of the circle.

-Optical errors (shade errors)
Shades are not optically flat.
AKA Prismatic Error

24
Q

P S I

Adjustable Errors (SEXTANT)

A

P S I

Perpendicularity Error
Index Mirror is not perpendicular to the plane of the instrument.

Side Error
Horizon mirror is not perpendicular with the plane of the instrument.

Index Error
Index and horizon mirrors are not parallel with each other when the arc is set to zero.

25
Q

list 9
Ways to find position

A
  • 3 Point Fix
  • Running Fix
  • Dipping Height/Horizon Ranges (Norries)
  • HSA (Sextant / Compass)
  • VSA (Sextant + Norries)
  • Contour lines (Echosounder) and visual bearing
  • 3 RADAR ranges
  • RADAR Range and Bearing (VRM + EBL)
  • GPS!
26
Q

How often to do a fix?
What is this dependent on?

A

Often enough that the vessel does not come into danger between fixes.

This is dependent upon:
- Ships Speed (RULE 6!!)
- Proximity to Navigational Hazards

27
Q

Explain a VSA

A

Visual bearing,
Angle (with sextant) between top of the structure and the waterline
Height of object,
Add HoT difference (MHWS).
»»>
Norries Nautical Tables - “Range by VSA”

28
Q

Explain a HSA

A

The angular separation between three points is measured by using the sextant horizontally to give us the angle.

On a chart
Using a station pointer or a protractor.

Position is where the two position circles intersect.

29
Q

Explain Leeway

A

The sideways drift of a ship
to leeward of the desired course.

30
Q

Explain CTS
(6)

A

When determining a course to steer, the tidal stream, current and the effect of wind/leeway must be predicted. Leeway is applied last.

  1. From last known position, extend ground track past destination.
  2. Apply tidal vector from the same last known position.
  3. Using a pair of dividers or compass mark out the distance you will travel in one hour across the intended ground track, this could be before or after the destination.
  4. Draw a line from the end of the tidal vector to the point the arc made on the ground track. This is the water track.
  5. Work out the leeway to be applied, add or subtract it depending on the direction of the wind.
  6. Once you have this course to steer (°T) then convert to compass(°C). –TVMDC

OOW 3000 (36 decks)

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