Radar plotting Flashcards

1
Q

Formula for Targets True Speed?

A

W - > A / Plotting Interval X 60

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1
Q

How to get CPA?

A

Right angle from relative line of approach to centre (+)

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2
Q

Formula for W -> O?

A

Speed / 60 X Plotting Interval

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3
Q

Formula for TCPA? (In minutes)

A

A -> n / O -> A X Plotting Interval

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4
Q

How to get Targets true course?

A

Ruler over W -> A and roll to middle (+)

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5
Q

How to get Aspect of target?

A

Extend line from W -> A and draw line from own vessel (+) -> A, aspect is degree between those two lines

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6
Q

What symbol do I put at CPA?

A

n

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7
Q

What symbol for O -> A?

A

(>)

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8
Q

What symbol for W -> O?

A

>

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9
Q

What symbol for W -> A?

A

> >

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10
Q

How do you find your speed reduction if you are given a CPA (on a VRM)?

A
  1. Basic report
  2. Arc out VRM from centre (+)
  3. DRAW out R.L.A (relative line of approach) from edge of circle back trough A, to W - > O line to find O1
  4. New speed = W -> O1 / PI x 60
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11
Q

How do you find your new CPA and TCPA if you reduce your speed?

A
  1. Basic report
  2. Calculate W -> O1 and plot
  3. Draw line from O1 -> A and extend
  4. Calculate new CPA (n1)
  5. Calculate new TCPA , A-n1 / O1 -> A x Plotting Interval
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12
Q

How do you plot an Instant alteration of course? (course given)

A
  1. Basic report
  2. Arc out W->O to Port or Stbd
  3. Draw new HDG from centre through W to arc, this is your new O1
  4. Join O1 to A for a new R.L.A
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13
Q

How do you plot a Course alteration for desired CPA?

A
  1. Basic report
  2. Arc out CPA circle (VRM) from centre
  3. Draw R.L.A from edge of VRM back through A and extend
  4. Arc out W->O to Port or Stbd
  5. Mark out O1
  6. Draw line W->O1
  7. Roll W-O1 to centre, that is your HDG
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14
Q

How do you plot delayed alteration of course?

A
  1. Basic report
  2. Find A1, O->A / PI x Delay
  3. Arc out W->O to Port or Stbd
  4. Take new HDG through W and find O1
  5. Join O1-> A in base plot then transfer to A1
  6. TCPA A1->n1 /O1->A x PI
  7. Add to A1 time
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15
Q

How do you plot desired CPA by delayed alteration of course?

A
  1. Basic report
  2. Arc out VRM
  3. Find A1
  4. Draw R.L.A from VRM edge to A1 then transfer to A and extend
  5. Arc out W->O
  6. Find O1
  7. Join W->O1
  8. Roll to centre, this the C/A
16
Q

How to find set, rate & drift on a radar plot?

A
  1. Identify fixed object
  2. Draw up a vector triangle with “another way” &laquo_space;towards W from A
  3. A-W is your tide
  4. Roll to centre to get tidal set
  5. Measure the length to get drift
  6. Calculate speed, A->W / PI x 60
17
Q

How to do a basic radar plot?

A
18
Q

How do you plot TTR? (Time to resume)

A
  1. Mark out CPA VRM
  2. Transfer original O->A to edge of VRM
  3. Where the two R.L.A meet is your TTR
19
Q

How do you plot delayed reduction of speed?

A
  1. Basic report
  2. Find A1
  3. Find O1 on original W->O line
  4. Draw new R.L.A through A->O1 then transfer through A1
20
Q

How do you plot desired CPA by delayed reduction of speed?

A
  1. Basic report
  2. Draw VRM
  3. Find A1
  4. Draw new R.L.A through edge of VRM to A1 then transfer through A to get O1 on W->O line
  5. Calculate new speed