exp Nav and RADAR Flashcards
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
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
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 less 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
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
What sections are in the weekly notice to mariners ?
- Explanatory notes. Publications list
- Admiralty notice to mariners. Updates to standard charts
- Reprints of NAV AREA 1 - navigational warning
- Updates to ADMIRALTY sailing directions
- Updates to ADMIRALTY lists of lights and fog signals
- Updates to ADMIRALTY List of radio signals
- Updates to miscellaneous ADMIRALTY nautical publications
- Updates to ADMIRALTY digital products and services
Principle of GPS
A global positioning system used for the purpose of navigation and detection of objects and places which is based on the ‘trilateration’ mathematical principle.
3 Satellites giving 3 position lines are required for a 3D fix.
4th satellite is required for time.
Usually on board GPS receiver is fixing from 6 or more satellites.
ECDIS - Standard display?
Used for normal navigation
A requirement that it can be selected AT ANY TIME WITH A SINGLE OPERATOR ACTION.
As well as the base layer contains-
Drying lines Buoys Other navigation marks Prohibited, Precautionary and restricted areas Separation and traffic routing
What projection would you for use for a great circle route ?
Gnomonic projection
How are ENCs updated and corrected?
Updates are issued weekly in electronic format and available via internet.
What publication can you find the meanings of chart symbols found on British admiralty charts?
NP….?
NP5011
Symbols and abbreviations used on admiralty paper charts
Define range discrimination
Refers to the ability of the set to show separately two similar targets on the SAME BEARING but on SLIGHTLY DIFFERENT RANGES
What are T’s and P’s and what is the procedure for marking them on a chart?
Temporary and Preliminary Notices.
Should be marked in pencil only together with the notice number and date.
Principle of a echo sounder
Transmission of a pulse of energy or signal
Which measures the time difference between transmission and return of energy/signal.
Time distance velocity calculation will give you the depth.
List 5 publications important to take on a passage
Sailing directions Ocean passages of the world Chart catalog Tide tables List of lights and fog signals
What is contained in section 2 of the annual summary of notice to mariners ?
Section 2:
Temporary and preliminary notices
5 different logs
Towed Impeller Electromagnetic Doppler Pressure Acoustic
Five ECDIS mandatory alarms
Crossing safety alarm Deviation from route Position system failure Approach to critic point Different geodetic datum
Function of Tune and Gain on a Radar
Tune adjusts the frequency generated in the receiver which will be mixed with the returning signals.
Gain controls the degree of amplification of the incoming signal.
Where is the best position for a gyro
Lowest possible
Centre line
Amidships if possible
List 5 mandatory alarms & 5 indications or warnings
Write them down!
MANDATORY ALARMS Crossing safety contour Deviation from route Positioning system failure Approach to critical point Different geodetic datum
INDICATIONS OR WARNINGS Information over scale Larger scale ENC available Different reference system Route planning access safety contour Route planning across specified area Positioning system failure Position Test failure
Describe ECDIS Base display?
List information that is found on this display
The absolute minimum information considered necessary for navigation such as -
Coast line Fixed structures Overhead wires Safety contour Scale, range and north arrow
NOT RECOMMENDED FOR NAVIGATION
However can be used when de-cluttering the screen to check ahead on a small scale
How often should you check the ships deviation
Change of watch
After ship has sat for long periods in one place
After shipyard - (structural changes, additions or alterations to vessel)
Difference between ECDIS and RCDS
ECDIS is a complete integrated navigation system, displays ENCs made up of multiple layers of information that can be interrogated.
RCDS displays raster charts and can be interfaced with GPS to show the vessel’s position.