Navigation Flashcards
The diameter through the equater is about _____ nautical miles longer than is the diameter through the North and South poles.
23
A ______ is geometric plane passing through the center of the earth, which divides the earth into two equal parts.
Great Circle
How large is the earth’s circumference?
21,600 nm
In every degree of arc in a circle, there are how many minutes?
60
For every minute of arc in a circle, there are how many seconds?
60
Parallel circles on the surface of the earth moving from the equator to the North or South pole?
Latitude
One degree of latitude is equal to how many nautical miles?
60
One minute of latitude is equal to how many nautical miles?
One
For normal boat navigation, what type of chart projection is used?
Mercator
When measuring distance in navigation always use what scale?
Latitude
A degree of longitude is only equal to 60 miles where?
At the equator
The prime meridian is 000 degrees and passes through where?
Greenwich, England
The 180 degree meridian is known as?
International Date Line
An imaginary line that intersects all meridians at the same angle?
Rhumb line
What are the 2 basic types of projections?
Mercator and Gnomonic
The difference between true and magnetic north?
Variation
Number on the chart represent soundings of the water depth at what tide?
Mean low tide
Tidal datum that is the average of all the low water heights observed over the National Tidal Datum Epoch (19 year average)?
Mean low water
Tidal datum that is the average of the lowest low water height of each tidal day observed over the National Tidal Datum Epoch (19 year average)?
Mean lower low water
Also known as fathom curves, these lines connect points of roughly equal depth and provide a profile of the bottom?
Contour lines
General chart scales are between?
1:150,000 to 1:600,000
Coastal Charts are produced at scales between?
1:50,000 and 1:150,000
Harbor charts are produced at scales larger than?
1:50,000
Small craft charts are produced at scales?
1:40,000 or larger
All slanted roman lettering on the chart is used to label what information?
All information affected by tidal change or current
Which color ink is used for most information on a chart since it is easier to read under red light?
Magenta
The line or mark scribed on the compass housing to indicate the direction in which the boat is heading?
Lubber’s line
The difference between magnetic and compass?
Deviation
The angular diffference between a compass direction and its corresponding true direction?
Compass error
Variation changes with the geological location of the boat and is caused by?
Earth’s magnetic field
________ changes the boats heading, and is not affected by the geographic locatin of the boat.
Deviation
“Swinging the ship” helps determine?
Deviation
To correct the compass, you ____ easterly errors, and _____ westerly errors.
Subtract, Add
Can Dead Men Vote Twice At Election
Compass, Deviation, Magnetic, Variation, True, Add Easterly errors
This hand-held line is used for ascertaining the depth of water and consists of a line marked in fathoms and weight of 7 to 14 pounds?
Lead line
What is the first fathom of a lead line marked by?
Wooden toggle
Second mark on the lead line (2 fathoms)?
Two strips of leather
Mark that indicates 3 fathoms and 13 fathoms on a lead line?
Three strips of leather
Mark that indicates 5 fathoms and 15 fathoms?
One white rag
Mark that indicates 7 fathoms and 17 fathoms on a lead line?
One red rag
One strip of leather with a hole on a lead line indicates what depth?
10 fathoms
20 fathoms on a lead line is indicated by?
Two knots
25 fathoms on a lead line is indicated by what?
One knot
What is inserted at the bottom of the lead line to help gather samples of the sea bottom?
Tallow
If a boat is traveling 10kts, how far will it travel in 20 mintues?
3.3 NM
Speed, Time, Distance formula?
60 D = S x T
The actual direction that boat’s bow is pointing at any given time?
Heading
Line drawn on a chart goin in one direction of a course?
Course line
The approximate position by advancing a previous position for course and distance only, without regard to other factors such as wind, current, and sea conditions?
Dead reckoning
A DR position modified by additional information, which in itself is insufficient to establish a fix?
Estimated position
A line of bearing to known object, which a vessel is presumed to be located on at some point?
Line of position
A position determined from terrestrial, electronic or celestial data at a given time with a high degree of accuracy?
Fix
A position determined by crossing LOPs obtained at different times?
Running fix
How many feet are in a nautical mile?
6,076 ft
The average speed in knots that must be maintained to arrive at a destination at any appointed time?
Speed of advance
The speed of travel of a boat along the track, expressed in knots?
Speed made good
A course followed on intended to be followed by a boat?
Track
The direction toward which the current is flowing expressed in degrees true?
Set
The speed of the current usually stated in knots?
Drift
Visual fixes on a chart are marked with?
Circle and time
Electronic fixes on a chart are marked by?
Triangle and time
DR positions are marked by?
Semi-circle and time
Estimated positions are marked by?
Square and time
A DR should be plotted when?
Every hour on the hour, every course change, every speed change, every fix or running fix, every bearing, and anything unusual.
A error of 1 degree at 1 mile will result in an error of?
100 ft
An ideal fix has how many LOPs?
3
LOP’s should have a seperation of at least ___, but not more than ___?
60 degrees, 120 degrees
The shorter the time interval between LOPs, the more ___ the running fix?
Accurate
Advancing a LOP for more than ___ minutes should be avoided?
30 minutes
Bearing used to keep a boat clear of hazardous areas in the vicinity of the track?
Danger bearings
Which fix is more reliable, visual or electronic?
Visual
The GPS is radio navigation system of how many DoD operated satellites?
24
GPS provides what two services?
SPS and PPS
Standard Position Service is accurate to a radius within ___ meters 99% of the time?
33
Precise Position System provides fixes accurate within ___ meters, and is limited to U.S. Federal government, allied military and civil users?
10
A GPS receiver must compute the range of at least how many satelittes?
4
What does ECINS stand for?
Electronic Charted and Integrated Navigation System
What does ECS stand for?
Electronic Chart System
What does SINS stand for?
Scalable Integrated Navigation System
What does ECDIS stand for?
Electronic Chart Display and Information System
Adequate back up arrangements for ECINS shall be transferable in how many fix intervals?
One fix interval
Manually entering visual and radar LOPs is considered what type of navigation?
Mode 2
In restricted waters, you should compare the primary positioning source to a backup source when?
At least every thrid fix
ECS is primarily used as a?
Situational awareness tool
Primary navigation should be transferable to paper plot within how many fixes?
One
Does SINS meet the standards for ECS?
No
When plotting with paper charts, fixes shall be plotted no more than ___ minute intervals?
30
When navigating within restricted waters, a fix shall be plotted a least every ___ minutes?
15
Do boats using SINS or ECS with an adequate primary position source need to plot paper fixes?
No
What form is compass deviation recorded on?
CG-2596
