ARPA Flashcards
Which of the following contributes to assessment of risk of collision?
- Relative motion line (CPA/TCPA)
- Aspect
- Amount of error in the calculations
What controls would you adjust if known targets were not being detected by RADAR?
- Gain
- Suppressions
- Range Scale
A RADAR contact will remain stationary on a relative motion radar display only when it is…
On the same course and speed as your vessel
The CPA of a contact on a relative motion RADAR may be determined:
After the contact has been marked at least twice over a period of at least a minute.
A RADAR display in which the orientation of the display is fixed so that North is always at the top of the screen is called a/an
Stabilized display
What inputs are required to maintain a North-up, True Motion display
Gyro course and Log speed
In addition to ARPA info, an ARPA user should take into account:
- The limitations of that info
- ROR
- The circumstances of the situation including external considerations
In restricted visibility what should you avoid when altering course for a vessel forward of your beam that you cannot see visually?
Altering course to port except in overtaking situations
When two ARPA equipped ships collide, which of the following is typically true?
Both vessels are likely to be found at fault.
When using ARPA, what should you consider in order to evaluate the info displayed?
Navigational constraints may require a target vessel to change course
Which of the following info is least dependent of ARPA processing?
EBL/VRM data
According to IMO, log and speed indicators providing inputs to ARPA equipment should be capable of providing:
The ship’s speed through the water
What is the min. number of targets that an IMO approved ARPA must track simultaneously?
20 targets
What is the lowest range scale that IMO requires ARPA facilities to be available on?
3 miles
According to IMO standards, the ARPA data display:
Should be visible to more than one observer in conditions of light normally experienced on the bridge by day or night.
Regarding the IMO requirement for past positions
All ARPAs can display both true and relative past positions
IMO requires ARPA to operate in relative motion with:
Either north-up or head-up or course-up display
According to IMO performance standards, what should an ARPA do to improve the standard of collision avoidance at sea?
ARPA should reduce the workload of observers by automatically providing information.
The ARPA facilities should be available on at least the following range scales:
3 or 4 miles and 12 or 16 miles
Two conditions needed for +/- steady state tracking
- Ownship maintains course & speed
- Target maintains course & speed
Which of the following is NOT a required operational warning on ARPA’s
Automatically Acquired Target
The NavLines displayed on an ARPA
Will drift when ARPA is sea-stabilized.
Gradual alterations of course will help the ARPA process data faster and provide more accurate info?
True or False
False
When observing a target’s past positions in TM what informatino can be quickly “gleaned”?
Target has changed course
Watchstanders can measure error in the ARPA presented information by using:
A plotting sheet or grease pencil plot on a reflection plotter.
You observe a target visually dead but is displayed on your RADAR at 5 degrees to STBD of the heading flash. How would you correct this?
Check the scanner for antenna misalignment.
When an ARPA-tracked target maneuvers:
First indication of a maneuver will probably be seen on a persistence or afterglow feature if your ARPA has one
Regarding ARPA errors, which of the following is true?
Relying on ARPA information can be dangerous
The vector displayed after 3 minutes of steady state tracking:
Represents the targets probable pas projected into the future
When operating a RADAR in fog, it is possible to have a limited effective range?
True or False
True
Which general statement concerning RADAR is NOT true?
The ability of RADAR to detect objects is unaffected by weather conditions
When operating a RADAR in fog RADAR ranges are less accurate?
True or False
False
You will get an alarm if target swap has occured.
True or False
False
If CPA/TCPA alarm is continually going off what should you do?
Adjust the limits to reflect the conditions
What input to an ARPA is needed for sea stabilized info?
RADAR input, gyro heading, and STW
What do ground stabilized true vectors intended to represent?
The recent track of a target’s motion over the ground projected into the future
When using navlines for nav, which stabilization method should be used?
Ground
When can Trial Manuever mode display inaccurate information?
When the ARPA (vectors) are ground stabilized.
When using a course-up stabilized display
The heading flasher does not move when you change course
Which of the following statements is TRUE regarding AIS?
AIS provides the other vessel’s identity, dimensions and navigational status regardless of visibility
Which of the following is true of the history display of past positions on an ARPA?
In the true presentation, it provides a quick visual check to determine if a vessel has changed course
If your speed input is incorrect, what effect would it have on your ARPA data?
True vectors would be incorrect
Cases in which your ARPA will alarm.
- Target initially detected in guard zone
- Target tracked who violates CPA/TCPA limits
- Lost target
- Tracked target who violates BCT/BCR
- ARPA failure
- Input loss
Your ARPA has two guard “trip wire” ring alarms. What is the purpose of the inner guard ring?
Warn of small targets that are initially detected closer than the outer guard ring
When ARPA’s are used in sea stabilized mode with true tracks, data relating to own ship’s motion is fed to the ARPA from the ___.
Speed log and gyro
When your ship is in a cross current, the NavLines on your ARPA screen will remain staionary, or near stationary, when you operate in
Ground stabilized mode
Which warning is required by the IMO performance standards?
A warning any time a target closes to a designated range or transits a zone, chosen by the observer.
Provided a target is not subject to target swap, the ARPA should continue to track an acquired target which is clearly distinguishable on the display for___
5/10 consecutive scans
Which of the following is NOT a commonly used term for ARPA’s target persistence of afterglow?
History dots
Conditions that would cause a fixed target to appear to have a true speed of more than zero.
- Centroid shift
- Current
- Incorrect speed input on ARPA
- Target swap