9. Navigation Flashcards
For overall planning on a long cruise, navigators should select a chart with
a SMALL scale that shows a LARGE area
The best binocular for use on a recreational vessel is
7 X 50
1 minute of latitude equals
1 nautical mile
Charts are being revised to use only the following datum for soundings
mean LOWER LOW water
Which of the following measures distances north or south of the equator?
latitude
Which scale of a chart should never be used for measuring distance?
LONGitude
The direction of a course is the angle it makes with a
meridian
You can find the amount of variation in your boating area by
looking at a compass ROSE on the chart of the area
If you measure the direction of a course line from a chart meridian, you have a
true direction
Variation is the difference between
True north and MAGNETIC north
Deviation is a compass error caused by
magnetic influences aboard your vessel
The technical term for the benchmark from which a marine chart’s vertical and horizontal measurements are made is
datum
Direction can be determined on a Mercator chart by using the
compass rose
A speed table is used to
determine speed from a tachometer reading
The vertical datum of a chart
helps you know how much clearance there is under a bridge
To correct a compass reading
add easterly variations
Mercator projections are made by projecting the earth’s surface onto a
cylinder
On a chart, shallow water is
light blue
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
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
