N&R Questions Flashcards
(162 cards)
What information should ARPA give within 3 minutes?
Full Report Time Bearing Range Target course Target speed CPA TCPA
What is meant by Geometric Dilution of precision?
Relates to orientation of the satellites around the receiver. If they give a shallow angle of cut between the position lines accuracy is downgraded.
How long should it take ARPA to give the user a relative vector on a acquired target?
1 Minute
What is CATZOC’S A1, A2 and B
Draw symbol
Sea floor coverage - for both A1 A2
Full area search undertaken
Significant seafloor features detected and depth measured
A1 position accuracy +/- 5m+5% (6 stars)
A2 position accuracy +/- 20m (5 stars)
B position accuracy +/- 50m (4 stars)
Why is horizontal datum important when plotting a GPS position on a chart?
A specific point can have different coordinates depending on the datum used.
List 5 items that could possibly be listed on a chart
Tidal Diamond Tables Notes Warnings Tables of tidal levels Crown copyright statement
Explain Parallel index lines?
Uses?
A PI is an adjustable electronic line on the radar display, set parallel to the ships track and at a set distance off.
Using a PI for coastal navigation is te safest and easiet method of keeping a ship on track
Great care should be taken in identifying and confirming reference points on the chart and on the radar and in verifying the radar range when using the parallel index.
List three different chart projections
Gnomonic
Transverse Mercator
Mercator
(Radar)
How can you confirm an echo is an indirect echo?
Turn gain all the way up and the radar will show the blind spot and this is where the indirect echo/target will be.
What two logs can measure speed of the ground ?
Doppler
Acoustic
What does MKD stand for and what are its disadvantages over a fully integrated AIS system
Minimum keyboard device
Extraction of details is tedious and prone to keying errors
3 Things that can be done to help minimize the effects of deviation on a binnicle
Three correctors used to minimise deviation are flinders bars and kelvins spheres for soft iron (induced magnetism) and vertical correctors for hard iron (permanent magnetism)
What information is within the annual summary of notices to mariners?
NP247
A database with details of history of corrections for all charts and sailing directions by the British admiralty or UKHO
Primary occasions and reasons for range adjustment within echo/depth sounder?
Give kHz values?
Different ocean depths
50khz wider pulse deeper waters but wont give as clear of as a picture
200khz narrower pulse shallow waters better detail, works better with aeration. Waters less than 100m
What effect will the sun’s radiation have on the Ionosphere? How will it effect the distance radio waves can travel?
It thickens the Ionosphere.
Radio reception distances are negatively affected during day time.
Better reception distances after sunset.
Effect on values shown by depth sounder in fresh water opposed to salt water and why?
Fresh water will indicate up to 3% more than the actual depth.
Acoustic signal travels faster in more dense water.
Main factors which might affect Radar target detection (5)
MASTS
Material- composition of the target
Aspect- Flat plate 90 degrees will give a good return, other angles can reflect energy away
Size- Greater the size, better return
Texture -flat better than rough
Shape - square is better than spherical
Define bearing discrimination
Refers to the ability of the set to show separately two similar targets at the SAME RANGE but SLIGHTLY DIFFERENT BEARINGS
Main components of Radar
Trasmitter
Scanner
Receiver
Display
ECDIS - Full display
Contains all the encoded chart objects
As the base display this is also not recommended for navigation as it clutters the display
What projections would you use for a great circle route
Gnomonic projection
Function of Gain Control on a depth sounder
Controls the sensitivity of the device and works on the amplifier, too much gain with a rocky seabed and multiple echoes are received.
5 ECDIS warnings or indications ?
Route planning across specified area Route planning across safety contour Information over scale Larger scale ENC available Positioning system failure Position test failure
Radar acronym for?
Radio detection and ranging
RAdioDectionAndRanging