Navigation / Charts Flashcards
1
Q
1minute latitude equals
A
1nautical mile
2
Q
Deviation is a compass error caused by
A
Magnetic influences aboard your vessel
3
Q
The benchmark from which a marine charts vertical and horizontal measurements is made
A
Datum
4
Q
Direction can be determined on a Mercator chart by using the
A
Compass rose
5
Q
A speed table is used to
A
Determine speed from a tachometer reading
6
Q
Position is determined by the intersection of 2 lops is
A
A fix
7
Q
For overall planning on a long cruise navigators should select a chart with
A
Small scale that shows a large area
8
Q
For overall planning on a long cruise, navigators should select a chart with
A
a SMALL scale that shows a LARGE area
9
Q
1 minute of latitude equals
A
1 nautical mile
10
Q
Charts are being revised to use only the following datum for soundings
A
mean LOWER LOW water
11
Q
Which of the following measures distances north or south of the equator?
A
latitude
12
Q
Which scale of a chart should never be used for measuring distance?
A
LONGitude
13
Q
The direction of a course is the angle it makes with a
A
meridian
14
Q
You can find the amount of variation in your boating area by
A
looking at a compass ROSE on the chart of the area
15
Q
If you measure the direction of a course line from a chart meridian, you have a
A
true direction
16
Q
Variation is the difference between
A
True north and MAGNETIC north
17
Q
Deviation is a compass error caused by
A
magnetic influences aboard your vessel
18
Q
The technical term for the benchmark from which a marine chart’s vertical and horizontal measurements are made is
A
datum
19
Q
Direction can be determined on a Mercator chart by using the
A
compass rose
20
Q
A speed table is used to
A
determine speed from a tachometer reading
21
Q
The vertical datum of a chart
A
helps you know how much clearance there is under a bridge
22
Q
To correct a compass reading
A
add easterly variations
23
Q
Mercator projections are made by projecting the earth’s surface onto a
A
cylinder
24
Q
On a chart, shallow water is
A
light blue
25
If you travel at a speed of 12 KNOTS for 10 MINUTES you will have gone how far?
2.0 Nautical miles
1 knot is 1 nautical mile per hour. 12 knots is a mile every 5 minutes
26
In an area with a variation of 12 degrees E, your heading is 130 degrees by your compass. The DEVIATION for this heading is 3 degrees W. What is your true heading?
139 degrees. 130 degrees, plus the VARIATION of 12 degrees EAST, MINUS the 3 degree DEVIATION WEST
27
What was the original light aid to Navigation?
Lighthouse
28
What is light nominal range?
The maximum distance at which you would see the light
29
What is dipping and rising distance?
There are tables containing this information and it is the point at which the light just appears on your horizon
30
What does Isophase mean?
On same time period each colour/dark
31
What does Occulting mean?
On longer than off (black flash)
32
What is Sectored Navigation?
Sectored lights will generally indicate the correct approach in a channel
33
What information about lights are found on charts?
Type of light (occulting, flashing, etc), how high the light is situated, har far the light will be visible for, and the colour of the light
34
If no colour of light is mentioned on the chart, what colour should you assume it would be?
White
35
Where would Moire Lights be located?
A marina entrance
36
What are Moire Lights?
Indicates when you are in the correct approach channel by displaying a vertical bar
37
Where are all depths on a chart measured from
chart datum, which is based on the L.A.T
38
What does L.A.T stand for?
Lowest astonomical tide
39
Where can you see chart datum on a chart
where the blue meets the green
40
what do the green areas represent on a chart
Areas that are below water at H.A.T but above water at the L.A.T
41
What does H.A.T stand for
Highest astronomical tide
42
What do the Buff coloured areas represent
Land
43
what do the blue areas represent, and what do the changes in colour mean
blue and white areas are water even at LAT. The different colours represent different depths
44
are contours the same on all charts
no, they vary depending on the area depicted
45
What is imporant to consider when using charted depths for navigation.
It's critical to add the hight of the tide on top to get accurate current depths
46
What is the bearing for north
000d
47
what is the bearing for north north east
022.5
48
what is the bearing for north east
045d
49
what is the bearing for east north east
067.5d
50
what is the bearing for east
090d
51
what is the bearing for east south east
112.5
52
what is the bearing for south east
135d
53
whats the bearing for south south east
157.5d
54
whats the bearing for south
180d
55
whats the bearing for southsouthwest
202.5d
56
what is the bearing for south west
225d
57
whats the bearing for west south west
247.5d
58
whats the bearing for west
270d
59
whats the bearing for west north west
292.5d
60
whats the bearing for north west
315d
61
whats the bearing for north north west
337.5d
62
what are all bearings on a chart relative to?
True north
63
how should bearings off a chart be written
Should be written with 3 figures, with (T) afterwords to signify its a true bearing. E.g. : 001d (T)
64
Where is the latitude scale found on the chart
its found on the left and right edges of navigation charts
65
where is the longitude scale found on the chart
its found on the top and bottom of the chart
66
what are latitude and longitude used for
as a grid they are used to pinpoint your position on the earth just like grid references on land maps
67
what is used to define position north and south from the equator
Latitude
68
How is latitude defined
Latitude north is any angle between The Equator and the North Pole using the centre of the globe as a fulcrum.
Latitude south is any angle between The Equator and the South Pole using the same fulcrum.
69
As you move north in the northen hemisphere how does latitude change
it increases
70
as you move north in the southern hemisphere how does your latitude change
it decreases
71
as you move south in the northern hemisphere how does your latitude change
it decreases
72
as you move south in the sothern hemisphere how does your latitude change
it increases
73
what is the minimum latitude value and where does it occur
0 at the equator
74
what is the maximum latitude value
90d N or S at the north or south pole
75
what must always be included with a latitude reading
a north or a south to defining which side of the equator you are on
76
What are the 2 uses of the latitude scale
firstly pinpointing position north and south, as well as measuring distances on the chart
77
what is the distance in 1degree of latitude
60 nautical miles
78
what is the distance in 1 minute of latitude
1 nautical mile
79
what is the distane in 1/10th of a minute of latitude
0.1 natuical miles or 1 cable
80
how far is 1 cable
0.1 nautical miles
81
how are latitude and longitude broken down
1 degree is 60 minutes, then decimal of minutes
82
what is a common error of reading the latitude or longitude scales
taking the nearest degree figure, when what you want is the nearest degree figure down the scale, otherwise you could be 60 miles out
83
How are minutes broken up on rya charts
depends on the scale, either .2 minutes or .1 minutes
84
what is the correct format for writing a lat or long
00d 00.00' N or S
85
when using a new chart what on the scale should you check
weather the minutes are divided into 5 or 10 increments
86
what is longitude
longitude is the distance east or west from Greenwich the boat is from.
87
where is 0 degrees longitude
0 degrees forms a line running from pole to pole through Greenwich England
88
as you move east from grenich what happens to longitude
it increases
89
what happens to the longitude as you move west from grenwich
it increases
90
what is the maximum longitude value
180d at the international dateline
91
should the longitude scale be used to measure distance
no
92
why can't you use the longitude scale for distance measuring
because the distance covered by each degree of longitude decreases as you move closer to the pole so it isn't consistent
93
what should always be included with a longitude measurement
East or west to indicate what side of grenich you are on
94
How should longitude be written
035d 10.000' W, always with 3 then 2 then 3 figures
95
What are dividers used for
measuring distance on a chart
96
when mesuring distance between two places where should you measure from
the circle at the base of the symbol
97
how would you obtain a distance between 2 objects on a chart`
take the deviders and set them to the distance between the objects on the chart, then without altering the setting of the dividers, place them on the latitude scale on the side of the chart. then read of the degrees minutes and decimal off to get the distance in NM
98
how would the dividers be used to obtain the longitude of an object on the chart
to get the longitude, use the dividers to measure the distance from the point in question to the nearest vertical line of the map. then without altering the dividers and place them on the point where the line in question meets the longitude scale. then read off the resultant longitude.
99
how would the dividers be used to obtain the Horizontal of an object on the chart
to get the longitude, use the dividers to measure the distance from the point in question to the nearest horizontal line of the map. then without altering the dividers and place them on the point where the line in question meets the longitude scale. then read off the resultant longitude.
100
what is the bezel of the plotter
the rotating disk used to take measurements in the centre
101
how should the bezel of the plotter be oriented
should always point north
102
how can you read a bearing from the plotter
align one edge of the plotter with the line on the chart to be measured, then rotate the bezel to point north
then you can read the bearing off using the arrow on the base of the plotter
103
What kind of bearing comes from reading the plotter
A True bearing
104
how can a bearing be drawn from an object using the plotter
take the true bearing to the object and set the bezel of the plotter to it. then place one edge of the plotter at the dot at the base of the thing you have a bearing to. then make sure the bezel is facing north, and draw your bearing along one edge
105
where are corections to a chart found
are at the bottom left located near customers information
106
Where do you get chart corrections?
notices to mariners, which have to be looked up and read
107
where can more up to date corections be found
the hydrographic office website, boating magazines, or the internet
108
where can you find information about the data used to make the chart
in the main chart text, typicaly in a large landmass
109
is a lead line reliable as a source of depth soundings for charts
less reliable than modern methods as they don't find sudon changes in depth
110
what warning is shown when starting up a chartplotter
a warning to only use it as an aid to navigation
111
what should you have on board in addition to a chart plotter
paper charts and the ability and knowledge to use them
112
What does SOG mean
speed over ground
113
What does COG Mean
Cource over ground
114
what does BTW Mean
bearing to waypoint
115
what does HDG stand for
heading
116
what are extension lines
lines that extend the cog or heading over the sea to better plan your course, they can also be set to show you where you will be in a given timeframe
117
what does chart detail do
displays more and less of the not navigational critical information
118
What does an arrival alarm on a Chartplotter do
sounds an alarm when you are within a certain radisu of a waypoint to allow for a course change or entering a marina
119
what does the depth min-max alarm do
it will sound an alarm if the vessel is in a great or lesser depth than expected
120
what is the XTE
Cross track error, how far the vessel is off cource
121
what are raster charts
high resolution scans of paper charts
122
what are the advantages of raster charts
The symbols, colour and information presented on the raster chart are identical to paper charts.
They are widely available and provide a cost effective way to convert information into an electronic format.
123
what are the disadvantage of raster charts
Due to the nature of their digitization they carry along with them any inherent errors in the paper charts and any errors that may have been introduced through the scanning process.
Zooming in distorts the image
no additional data with the chart to help plan your passage
124
what are vector charts
Vector charts are constructed of lines, points or areas which not only provide a graphic representation of charted features, but also include an associated data base.
125
what are the advantages of vector charts
The database provides 'layers' of information on the electronic chart which allow the user to manually or automatically query a specific3 area for additional information.
Chart plotters have a facility to zoom in on a vector chart and get more information, whereas when zooming in on a raster chart the same image just gets bigger.
The layers of data on a vector chart can be read by an ECDIS and depending on the configuration, Alarm parameters can be set to warn of approaching hazards such as shoal water or an underwater obstruction.
Individual points or areas on the vector chart may be queried by the user such as navigation marks, sounding data in a chosen location, anchorage information, traffic schemes etc.
126
why is chart plotter detail setting inportatn
it might not show some critical information
127
Underwater rock of unknown depth, dangerous to surface navigation
128
Rock awash at chart datum
129
Rock which covers and uncovers, height (underlined) means above chart datum
130
Magenta tear drop with star not filled in
Major lighthouse
131
Magenta tear drop with star filled in under it
Minor light
132
Rocks
133
+
Underwater Rock
134
True or False?
It is a legal requirement for commercial craft to carry updated paper charts as well as any electronic versions
True
135
What are the two types of charts?
Raster Charts
Vector Charts
136
What are Raster Charts?
Scanned copies of original paper charts
137
What are Vector Charts
Built up from digital information
138
Where can you find the date on a chart to ensure you are using an up to date chart?
Bottom left
139
Where can you find all changes over the last 7 years?
UK Hydrographic Office
140
Name two ways you can update electronic charts
CD-ROM
Internet subscription service from manufacturer
Purchasing a new cartridge for the plotter
141
What are the three projections used?
Mercator, Transverse Mercator and Gnomonic
142
What is a benefit of Mercator?
Lines of constant bearing (rhumb lines) will appear as straight lines, useful for steering compass courses
143
What is Transverse Mercator used for?
Large scale charts and harbour plans
144
What is Gnomonic projections used for?
Polar charts and planned ocean crossings
145
What colour is shallow water on charts?
Blue
146
What is this icon?
147
What is this buoy?
148
Where is Salthill and what is outside it?
149
What is at the entrance to Poolbeg?
150
what is magnetic variation
the difference in bearing caused by the difference between true north and magnetic north
151
what is the magnetic deviation
the difference between true north and north on a compass due to ferrous metal objects on the vessel
152
if the magnetic variation is west, do you add or subtract from the true bearing
Added
153
if the magnetic variation is east, do you add or subtract from the true bearing
Subtract
154
when a course is measured on a chart, what kind of course is it
True
155
When a course is measured from a compass at the bow of the boat what kind of course is it
Magnetic
156
When a bearing is measured from the cockpit what kind of bearing is it
compass
157
what is taken into account converting a bearing from true to magnetic
Magnetic variation
158
what is taken into account converting a bearing from magnetic to compass
Magnetic deviation
159
what is taken into account converting from a true bearing to a compass bearing
magnetic variation and magnetic deviation
160
what is magnetic variation caused by
magnetic north being in a different location than true north
161
what must be checked when working with magnetic variation
that you are using the correct variation for the area you are sailing in
162
where can variation information for an area be found
on the compass rose on the chart in question
163
when is the one time that variation is 0
when true north, magnetic north and the vessel all are on one great circle.
164
what small things can affect variation
geologic features such as deposits of iron or industrial equipment
165
what is the number in brackets with a variation reading on an admiralty compass rose
the yearly change in variation
166
how is yearly variation change measured
in minutes, or 1/60th of a degree
167
how would you work out the current variation
take the variation and yearly change of the charts. check the chart publication date, then multiply the yearly change by years from publication, to get the change in magnetic variation since the chart was published. this can then be added to the charts magnetic variation to get the most up to date variation
168
Where is the Magnetic North Pole right now?
Canada
169
How far does the Magnetic North Pole move each year?
40km
170
What is Variation?
The difference between the Magnetic North Pole and the True North Pole
171
Where will you find the Variation?
On the Compass Rose
172
If the Variation is East do you add or subtract from the True North Pole?
Add
173
If the Variation is West do you add or subtract from the True North Pole?
Subtract
174
How many minutes in one degree?
60
175
What is Deviation?
Stray magnetic fields in the vicinity like heavy metal from the engines can give inaccurate compass readings
176
What is it called when you check the compass and how often should this be done?
Swinging the compass and annually
177
True or False
Hand bearing compasses are treated as having zero variation
True
178
How often should you check for deviation?
Once a year
179
True or False
The original magnetic compass is the only compass not to require power
True
180
What is the Fluxgate Compass?
Two or more coils, small current detects the earth's magnetic field
181
True or False
A magnetic compass is always carried as back up
True
182
What is the ship's compass?
a large compass at the helm of the ship, often used for steering.
183
What is the advantage of a fixed compass?
as it doesn't move around the vessel it can be corrected for magnetic deviation.
184
How would you work out your vessels magnetic deviation?
you would turn the boat through 360 while on a set transit, and compare readings from the ship's compass to the known bearing of the transit, allowing you to correct the compass.
185
what is a hand bearing compass?
a compass that has a sight, which allows you to take bearings to visible objects.
186
what are two good uses of a hand bearing compass?
1) taking bearings to fixed objects to get a position fix
2) taking constant bearings to an approaching vessel to determine collision risk.
187
what must be carefully considered when using a hand bearing or other mobile compass, and what can be done about it?
the magnetic deviation on the ship varies across the deck, so the bearing could be inaccurate. to combat this, the compass should be used as far away from any ferous metals or magnetic objects that could cause deviation.
188
what is a fluxgate compass?
a fluxgate compass is an electronic compass that senses the magnetic field of the earth electronically.
189
what are the advantages of a fluxgate compass?
it has no moving parts as it just uses electronics to sense the magnetic field. The compass bearing can be digitised and used on chart plotters or autopilots. it can be electronically corrected for deviation.
190
How do we measure things on the surface?
Angular Management
191
How many minutes is one degree?
60 minutes
192
What is the line between two points called?
A great circle
193
What Latitude is the equator?
0º
194
What is one tenth of a minute called?
A cable
195
How many nautical miles is one minute?
One nautical mile
196
Is distance measured with Latitude or Longitude?
Latitude
197
What is a Meridian?
They are great circles which start at one pole and cut the equator at right angles and carry on to the other pole
198
What is the International Date Line?
This is where Meridians meet at 180º East or West
199
True or False?
The Date Line is at 180º East so West only goes up to 179º
True
200
How wide are Marine Time Zones?
15º except at 180ºW around the Date Line where are two zones of 7.5º
201
True or False?
The zone number tells you what to do to get UT
True
202
What does UT stand for?
Universal Time
203
What does GMT stand for?
Greenwich Mean Time
204
True or False?
Latitude is given in North and South and Longitude is given in East and West
True
205
What is Navigation Distance measured in?
Miles
206
What does the Log record?
How far a ship has gone through water
207
True or False?
Nautical Miles per hour is the Knot
True
208
Name the two fundamental types of Logs
The towed variety
The through hull fitting
209
True or False?
Direction is referred to using 360º notation
True
210
What is the variation for Dun Laoghaire?
What does it change by?
