Radar plotting Flashcards
Formula for Targets True Speed?
W - > A / Plotting Interval X 60
How to get CPA?
Right angle from relative line of approach to centre (+)
Formula for W -> O?
Speed / 60 X Plotting Interval
Formula for TCPA? (In minutes)
A -> n / O -> A X Plotting Interval
How to get Targets true course?
Ruler over W -> A and roll to middle (+)
How to get Aspect of target?
Extend line from W -> A and draw line from own vessel (+) -> A, aspect is degree between those two lines
What symbol do I put at CPA?
n
What symbol for O -> A?
(>)
What symbol for W -> O?
>
What symbol for W -> A?
> >
How do you find your speed reduction if you are given a CPA (on a VRM)?
- Basic report
- Arc out VRM from centre (+)
- DRAW out R.L.A (relative line of approach) from edge of circle back trough A, to W - > O line to find O1
- New speed = W -> O1 / PI x 60
How do you find your new CPA and TCPA if you reduce your speed?
- Basic report
- Calculate W -> O1 and plot
- Draw line from O1 -> A and extend
- Calculate new CPA (n1)
- Calculate new TCPA , A-n1 / O1 -> A x Plotting Interval
How do you plot an Instant alteration of course? (course given)
- Basic report
- Arc out W->O to Port or Stbd
- Draw new HDG from centre through W to arc, this is your new O1
- Join O1 to A for a new R.L.A
How do you plot a Course alteration for desired CPA?
- Basic report
- Arc out CPA circle (VRM) from centre
- Draw R.L.A from edge of VRM back through A and extend
- Arc out W->O to Port or Stbd
- Mark out O1
- Draw line W->O1
- Roll W-O1 to centre, that is your HDG
How do you plot delayed alteration of course?
- Basic report
- Find A1, O->A / PI x Delay
- Arc out W->O to Port or Stbd
- Take new HDG through W and find O1
- Join O1-> A in base plot then transfer to A1
- TCPA A1->n1 /O1->A x PI
- Add to A1 time