Test 2 Flashcards
(208 cards)
1
Q
How does inclement weather effect radar?
A
Max range of contacts is reduced and unwanted echoes are produced by sea return
2
Q
How do you reduce unwanted sea clutter?
A
Reduce receiver gain or switch to a shorter pulse length
Best option is to turn up STC
3
Q
At what distance does sea return disappear?
A
6-8 miles
4
Q
STC
A
Sensitivity time control
5
Q
The higher the vessels radar antenna above the water,
A
The greater the sea clutter effect
6
Q
Radar can be used to determine the direction of true wind (even at nite) by
A
Observing the area of sea clutter on the radarscope
7
Q
Rain, hail, and snow may return echoes that appear as
A
Blurred or cluttered areas
8
Q
Heavy precipitation tends to
A
Absorb pulse strength and decrease maximum detection range
9
Q
FTC
A
Fast time constant
10
Q
FTC control reduces the length of
A
Pulse echoes
11
Q
Does FTC have any effect on actual length of transmitted pulses?
A
No
12
Q
FTC is sometimes referred to as
A
Differentiator
13
Q
In inclement weather what radar is best?
A
10cm
14
Q
If a suspected target is within an area of precipitation,
A
Use the FTC circuit to reveal stronger echoes
15
Q
If a suspected target lies beyond precipitation,
A
Temporarily increase receiver gain
16
Q
Land masses are generally recognizable because of the
A
Steady brilliance of the relatively large areas
17
Q
Weak echoes received at low tide
A
Disappear at high tide
18
Q
What man made structures make good radar targets?
A
Breakwaters Jetties Piers Bridges Building
19
Q
Small boats can be distinguished from buoys by
A
Plotting
20
Q
What enhances otherwise poor target response of buoys and small boats?
A
Radar reflectors
21
Q
Radar reflectors send echoes
A
180* back the direction it came from
22
Q
Racon
A
Radar beacon
23
Q
A racon is a
A
Small transceiver
24
Q
Racons register on the PPI as
A
Morse code signal
25
Modern racons that respond to both x and s band radars are called
Frequency agile
26
Because of beam width distortion,a straight or nearly straight shoreline often appears
Crescent shaped
27
Pulse length distortion increases as the angle between the
Beam axis and shoreline decreases
28
Indirect or false echoes are caused by
Reflection of the main lobe of the radar beam off ships structures such as stacks and kings posts
29
Multiple echoes may occur when a strong echo was received from another ship at
Close range
30
FTE
Falls targets ellimination
31
How is spoking distinguished from interference effects ?
The lines are straight on all range scale settings, and are lines rather than a series of dots
32
Spoking indicates a need for
Maintenance or adjustment
33
What can also indicate a need for maintenance on the PPI?
Serrated range rings
34
ARPA
Automatic radar plotting aid
35
ARPA applies to radar units that allow
Automatic acquiring, tracking, plotting of radar targets
36
The purpose of ARPA is
Collision avoidance
37
Observing a vessel’s course and speed of referred in
Relative motion
38
ARPA error is based on
+/-10° of roll
39
ARPA accuracy values required after one minute
95% probability
40
EPA
Electronic plotting aids
41
Smaller vessels not required to have ARPA are frequently fitted with
EPA
42
What did the IMO implement in 1990?
The two observer requirements for ARPA
43
What was the beneficial consequence of the two observer requirement?
No more hooded radars
44
What is required for ARPA to track a target?
Sufficient signal strength and persistence
45
What is defined by the pulse length and beam width?
Resolution cell
46
CFAR
Constant false alarm rate
47
If there are more than 20 targets that meet the CFAR criteria, ARPA will select the
20 most dangerous targets according to range
48
What will happen when ARPA selects targets for tracking?
a visual and audible alarm will sound
49
When ARPA is tracking a target it is performing mathematical calculations based on
Past target positional data to determine target motion
50
What are the two purposes in determination of target motion?
Provides the radar observer with target information necessary for collision avoidance, and move the tracking gate to allow tracking to continue
51
ARPA calculates target motion based on past positions through a process known as
Least squares regression or smoothing
52
Tracker cells usually measure less than
Half degree in angular measure, and no more than .025nm in range
53
As tracking continues and more positions are recorded, the measure of confidence in the predicted track of the target increases and a
More accurate presentation of actual target motion is provided
54
A smaller tracking gate has the advantage of less likelihood of target last through
Rain clutter, sea clutter, proximity to other targets
55
What is a disadvantage of a small tracking gate?
Possible loss of the target
56
When a target is not found during any successive antenna sweep,
The size of the tracking gate will increase to find it
57
The computer algorithms that controls movement and size of the tracking gate is known as
Rate aiding, or Kalman filtering
58
When will ARPA calculate accurate relative data?
Within one minute from the start of tracking
59
When will ARPA provide true data?
After about two minutes of tracking
60
What happens after three minutes of tracking?
The oldest data is erased
61
If automatic tracking, the number of targets to track must be at least
20
62
What is the minimum number of target to track if manually tracking?
10
63
Where do vectors begin?
At the contacts present position
64
The length of a vector depends on the
Time that the operator enters
65
The primary function of marine radar is_________, not__________
Collision avoidance; navigation
66
Relative vectors do not give an indication of
Target aspect
67
In confined waters, relative vectors are less useful. In other words use
True vectors
68
VRM
Variable range marker
69
EBL
Electronic bearing line
70
Do faulty gyrocompass or speed log inputs have any affect on the accuracy of the relative vector presentation?
No
71
ARPA should normally be set on
True vectors
72
Is accuracy of true vectors seriously degraded by any input error from the speed log or Gyro?
Yes
73
A 1° Gyro error is for practical purposes
Insignificant
74
A 1 knot error of speed input can lead to
Disaster
75
Acura target tracking depends on a
Steady state condition
76
What are main causes of vector instability?
A target with too little time in track; the contact maneuvers; own ship maneuvers; contact with poor radar target response; fluctuating Doppler speed login put; unstable or hunting gyrocompass
77
Any large course or speed change requires
A minute or so to settle before any further collision avoidance assessments are made
78
What allows a navigator to see predicted changes in all tracked relative plots resulting from a proposed maneuver by their own ship?
Trial maneuver
79
What are the steps in trial maneuver?
Determine any constraints; select a new CPA; select relative vectors; extend vector time to determine collision of desired CPA; turn on trail maneuver and set MX point; Adjust controls for ship or speed to move the new relative motion line; read the new course and/or speed after the vectors of settled; Exit trial maneuver and give command to alter course and or speed
80
Target past positions can be displayed by a series of at most
Four dots equally spaced in time
81
When will ARPA emit an alarm to denote that a target is lost?
When no evidence of the target is found after five successive sweeps of the antenna
82
What does ground stabilize use as a frame of reference?
Land features
83
What is also used to ground stabilize the ARPA?
GPS
84
Integrated ECDIS and ARPA use
GPS ground stabilization
85
True vectors represent targets and own ship courses and speeds through the water
See stabilized
86
Relative vectors in both ground and sea stabilized are
Identical
87
a polygonal shape placed around a contact that indicates a range of coarse for your ship not to steer if it is desire to maintain a minimum desirable CPA is called
(PAD) predicted area of danger
88
When is PAD best used?
In open ocean with a few targets
89
What is the only commercial vessel exempted from AIS?
Fishing vessel
90
In what band does AIS broadcast
VHF
91
What is the range of VHF?
20–30 miles
92
AIS can be invaluable for warning of contacts
Well beyond normal radar range
93
AIS may continue display a targets location even if it becomes
Shadowed by intervening land or obscured by rain clutter
94
The greatest asset that AIS provides is the ability to make
Positive identification of target vessels on the radar screen
95
When a target vessel is rolling in pitching and moderate to heavy seas, the point of greatest target response may shift location over the targets surface due to the constantly shifting target aspect.
Glint
96
Glint standard deviation =
1/6 the length of ship
97
Bearing error due to
Rolling of own ship
98
Range error due to
Own ship rolling
99
What is the most common source of all ARPA errors not due to miss interpretation by the radar observer?
The Doppler speed log
100
The accuracy of the Doppler speed log output should be
Frequently monitored by the observer
101
Information transferred from a week target to a stronger target or land feature if they appear in the same tracking gate is known as
Targets swap
102
A big shift in the point of target response, as when a target turns in the aspect changes, causes the track vessel to appear as if it sped away is known as
Centroid shift
103
A complacent observer is open to making
Careless mistakes
104
SAR
Search and rescue
105
What are the four search and rescue patterns?
Expanding square; sector; parallel; ship/aircraft coordinated
106
The US Coast Guard operates how many racons?
About 80
107
Who other than the US Coast Guard within the United States operates racons?
Owners of oil platforms
108
RACONS Are used to
Mark like houses in navigation buoys; navigate spans under bridges; identify centerlines and turning points; offshore oil platforms and other structures including approximately 35 in the gulf of Mexico
109
To avoid masking important radar targets beyond the beacon, racons
only operate
Part of the time
110
Racons Usually operate in what band?
3 cm x band
111
A microsecond is
One millionth of a second
112
A nanosecond is
One billionth of a second
113
How far can light travel in one nanosecond?
11.8 inches
114
What is the range of a RACON?
Line of sight, normally over 15 nautical miles
115
RACONS transmit and approximately___microsecond Morse encoded response less than_____nanoseconds later back to the radar on that frequency.
25; 700
116
What on a radar could mask a RACON return?
Anti-clutter rain control
117
A wideband Beacon which transmit continuously on the radar bands without having to be triggered by an incoming radar signal.
Ramark
118
Are RAMARKS used in the US?
No
119
SART
Search and rescue transponder
120
A SART will only respond to a
9 GHz X band (3 cm wavelength) radar
121
What range well an x band radar Trigger a SART?
Eight nautical miles
122
When a SART detects a signal it will immediately transmit
12 pulses on the same frequency
123
You would expect to find two radar’s installed on vessels of what description?
Greater than 10,000 GRT
124
SOLAS compliant radar’s must be capable of operating in the
Stabilized mode
125
Is it a requirement of SOLAS that, when in or near restricted visibility, a continuous watch of the radar be maintained?
No, it is only a recommendation
126
What type of beam width does an antenna wide in the horizontal dimension produce?
Narrow
127
Describe what would happen to a target on your radar when it enters an acquisition zone
The target would be automatically acquired triggering a visual and audible alarm
128
Radar observer endorsements are required on licenses for US deck officers on vessels of
300 gross tons more more equipped with radar
129
What must be violated before an alarm is activated on a danger target?
CPA and TCPA
130
What are the effects of electromagnetic radiation?
Refraction, reflection, attenuation, defraction
131
When making landfall the 00W may increase the range scale to
Assist in determining the distance of landfall
132
When increasing the range the 00W may need to
Adjust gain and clutter controls
133
When a target has been found be sure to
Crosscheck the information with all available means
134
Landmasses may have descriptive layout of the land according to the chart, but may become masked (or distorted) due to the
Width of the beam Width
135
Targets located on the other side of a target may be lost due to the loss of pulse detection, which is called
Shadowing
136
Radar conspicuous target is one which produces a
Good response that can be positively identified
137
What are the two techniques to aid in determining position?
Line of position (bearing); circle of position (range)
138
A line indicating a series of possible positions of a craft, determined by observation or measurement.
Line of position
139
True bearing is the bearing relative to
True North
140
Relative bearing is a bearing relative to
Heading or to the craft
141
What are the two factors that should be taken into account when determining the exact location of another target?
Gyro error and beam width error
142
What is more accurate for obtaining fixes, radar bearings or radar ranges?
Radar ranges
143
Which is more accurate, a Gyro bearing or a radar bearing?
Gyro bearing
144
What is vital to avoid navigation errors?
Crosschecking one method against the other
145
What is a method that allows for constant monitoring of the vessels position?
Parallel indexing
146
Are reflection plotters common?
No
147
ECDIS
Electronic chart display information systems
148
An ENC is an
Electronic chart issued by a national hydrographic authority
149
Up to date chart requirements are regulated by
V/19, and V/27 or the 1974 SOLAS convention
150
ENC’s produced by a government hydrographic office
Official
151
Charts produced by private companies
Unofficial
152
A commercial electronic chart system not designed to satisfy requirements of the IMO
ECS
153
An ECS HAS TO be used in conjunction with
Paper charts
154
What else can be considered an ECS?
A cell phone
155
The digital database which electronic charts are produced
Electronic Chart Data Base
156
The hydrographic data base from which the ENC is produced
Electronic Navigation Chart Database
157
What is considered to be equivalent to a paper chart
SENC
158
If just one of the official requirements for an ECDIS are not met,
The system has the status of an ECS
159
Benefits of an ECDIS
Reduced workload for the navigator; navigation in real time; automatic route monitoring; automatic track control; prediction for special maneuvers; availability of chart at night without night vision loss; access to additional information resources
160
Disadvantagesof ECDIS
Too much info on screen; submenus complex; chart size reduced; symbols may be misinterpreted; complacency
161
What is becoming the essential tool for the watch keeping officer?
ECDIS
162
What is the most complex system on the bridge?
ECDIS
163
ECDIS equipment consists of
Hardware
Operating software
Digital hydrographic data in the form of ENC
ALPHA numeric info
164
When did the IMO define performance standards for ECDIS?
1995
165
IHO
International Hydrographic Organization
166
IEC
International Electrotechnical Commission
167
S-57/S-100
Transfer protocol
168
S-61
Raster nav charts
169
S-52
Specs for content and display
170
S-63
Encryption
171
S-64
Testing standards
172
ECDIS MUST BE WIRED TO
GPS, gyrocompass, speed and distance measuring device
173
What are the two ways to back up an ECDIS
Second ECDIS
| Paper charts
174
How long can power be interrupted without reinitializing the ECDIS?
45 seconds
175
ENC charts are also called
Vector charts
176
What charts are required by ECDIS?
ENC
177
A single vector chart is called a
Cell
178
Raster data files tend to be
Large
179
Raster charts cannot take the place of
Paper charts
180
If an ECDIS uses raster charts it operates in the
ECS mode, And you must have a paper chart back up for that area
181
MRA
Mutual recognition agreement
182
What are the 2 ECDIS training types?
Generic and equipment specific
183
Compliance with regulatory ECDIS requirements will be checked by
Port state control
184
The level of proficiency necessary for proper performance of the ECDIS functions on board a ship
Standard of competence
185
Raster
Scanned and passive image of a paper chart
186
Vector
Interactive chart reacting to digital analysis by object
187
Where is RNC permitted?
Only were no official vector chart exists
188
WGS 84
World Geodetic System
| Standard for use in cartography geodesy and navigation
189
IMO requires
North up presentation
190
Ship and targets motions are based on sensors that deliver course through the water and speed through water
Water stabilized
191
Route monitoring is used in
Ground stabilized mode
192
Collision avoidance must be used in
Water stabilized mode
193
What occurs when ENC is displayed at a larger scale than intended by the compilations scale
Over scaling
194
Minimum level of chart info that has to be displayed
Base display
195
Base display is not designed for
Navigation
196
Common mode for route planning and route monitoring and contains minimum required information for navigation
Standard display
197
Shows all info relating to chart
All display
198
What are the three levels of display for system information
Base, standard, full
199
SCAMIN
Scale minimum
| Sets the scale below that an object no longer be displayed on the screen automatically
200
ECDIS Can be viewed as
Primary or secondary display
201
What are the 2 available color schemes?
Two depth shades
| Four depth shades
202
Line between navigable and unnavigable sea areas
Safety contour
203
Dark blue
Shallow waters
204
Medium blue
Risk of grounding
205
Light blue or grey
No danger of grounding, but other restrictions can limit speed
206
White
Very deep waters no sailing restrictions
207
What is selected by the murdered provide a more clear indication of unsafe spot soundings
Safety depth
208
Bathymetric inlays
Present a more accurate presentation of under water features
