Navigation and Aids to Navigation Flashcards
The intersection of two or more Lines of Position is called:
Estimated Position
Fix
Waypoint
Dead Reckoning position
Fix
A fix is the intersection of two or more Lines of Position (LOPs), often taken by shooting compass bearings to known objects or lining up two fixed objects on a chart. Ref: BCME p 124
To measure distance on a Mercator chart, use:
Latitude scale, where 1 degree = 1 nm
Longitude scale, where 1 degree = 1 nm
Latitude scale, where 1 minute = 1 nm
Longitude scale, where 1 minute = 1 nm
Latitude scale, where 1 minute = 1 nm
On a Mercator projection chart, lines of latitude and longitude are perpendicular to each other. The latitude scale is constant, where 1 minute of latitude equals 1 nautical mile. Ref: BCME p 120, 125
The distance between Waypoint A and Waypoint B is 7.5 nm. Departing A at 0900, you sail a straight course and arrive at Point B at 1015. What was your Speed over Ground?
5.5 kts
6.5 kts
6.0 kts
7.5 kts
6.0 kts
The time enroute is 1015 - 0900 or 1.25 hrs. Use the formula Distance = Speed x Time, or Speed = Distance/Time + 7.5 nm / 1.25 hrs = 6 kts. Ref: BCME p 125.
The course between Waypoints C and D is 020M. You sail on a port tack from C to D, holding a steady heading of 020M. At the halfway point, you find yourself one mile right of course. What is the most likely reason?
You didn’t account for Variation when steering 020M
You didn’t account for Deviation when steering 020M
Leeway and current set you east of your desired course
Leeway and current set you west of your desired course
Leeway and current set you east of your desired course
Your heading 020M is not keeping you on your planned course 020M, but you are being set right (east) of course. Leeway and current are the most likely reasons. Since all references are Magnetic, variation and deviation are not factors. Ref: BCME p 130, 136
Your boat has a 5’ draft, and you wish to cross a sandbar with a 1’ safety margin to enter a harbor. The sounding on the chart shows minimum 4’ on the sandbar, referenced at MLLW. When can you enter the harbor?
Only during a Neap Low Tide
When the tide exceeds 1’ above datum
When the tide exceeds 2’ above datum
Never, your boat’s draft is too deep
When the tide exceeds 2’ above datum
Your boat’s draft + safety margin = 6’. To clear the sand bar, you’ll need 6’ of water: that’s 4’ (sounding referenced from datum MLLW) + 2’ tide. Ref: BCME p 138-139
Soundings on a nautical chart are referenced from a vertical datum, and may be expressed in these units:
Feet, Meters, Fathoms
Meters, Fathoms, Leagues
Kilometers, Nautical Miles
Leagues, Kilometers
Feet, Meters, Fathoms
Water depths on a chart are called soundings, and can be expressed in units of feet, meters, or fathoms. It’s im-portant to check your chart title block to determine which units you have. BCME p 121
You plan to take compass bearings on two objects for a visual fix. Object A is off your bow, Object B is off your beam. How should you organize your bearings?
Shoot A one minute before fix time, then shoot B one minute after fix time
Shoot A at fix time, then shoot B as soon as possible later
Shoot B at fix time, then shoot A as soon as possible later
Shoot B one minute before fix time, then shoot A one minute after fix time
Shoot B at fix time, then shoot A as soon as possible later
Bearings taken on objects on the beam change more rapidly than those on bow or stern, so take those at fix time for a more accurate fix. Ref: BCME p 133.
Which speed would allow you to calculate the most accurate ETA to a waypoint?
Boat Speed
Speed Over Ground
Apparent Wind Speed
True Wind Speed
Speed Over Ground
Your estimated time of arrival (ETA) is based on your speed to a destination. Boat speed is speed through the wa-ter, and does not account for current. Since Speed Over Ground is based on GPS, it’s a more accurate speed to use for an ETA. Ref BCME p125
What is the tidal range for 14 June?
10.00’
9.55’
8.80’
8.31’
9.55’ (needs a picture)
Tidal range is the difference between high and low tide for the period. For 14 June, range is 10’ - 0.45’ = 9.55’. Ref: BCME p 138
At which of these times would you expect the greatest rate of tidal change?
0200
0500
0900
1500
0500 (needs a picture)
The greatest rate of tidal change is typically mid-cycle, as reflected by the non-linear tidal curve. For July 14, mid-cycle is about 0500 and 1200. 0200 is close to high tide, and 0900 is close to low tide. Ref: BCME p 138-139
What type of tidal current would you expect between 1100-1300?
Flood
Ebb
Slack
Stand
Flood (needs a picture)
1100-1300 is during the rising tide, which is associated with a flood current. Ref: BCME p139.
Your Course over Ground is 090T and you see a black and yellow buoy with 2 black triangles pointed up dead ahead. What should you do?
Reverse direction immediately, isolated danger ahead
Turn to starboard, safe water is south
Turn to port, safe water is north
Maintain your heading, but avoid this weather buoy
Turn to port, safe water is north (danger marker picture)
The topmark of a cardinal mark indicates which direction safe water lies from a hazard. Two triangles pointed up indicates that safe water lies to the north. Ref: BCME p.123.
You are entering a harbor, and wish to take the preferred channel (IALA B). You see a red and green banded buoy ahead, with red as the topmost band. What type ATON is this, and how do you treat it?
Preferred channel mark, keep it to starboard
Preferred channel mark, keep it to port
Safe water mark, deep water on either side
Isolated danger mark, keep it to port
Preferred channel mark, keep it to starboard (channel marker picture)
A preferred channel mark indicates a junction, and has red and green bands. The top-most band indicates how the mark should be treated if entering the preferred channel. If the top band is red, keep it to starboard if you are entering a harbor (red right returning). Ref: CCME p 92-93
What Aid to Navigation does Fl R 4s describe?
A red day beacon
A lighted fixed beacon flashing red every 4 seconds
A lighted red buoy flashing red every 4 seconds
A lighted red buoy flashing red 4 times per second
A lighted red buoy flashing red every 4 seconds (needs a picture)
Fl is flashing, R is red, 4s is the light interval. A fixed beacon would include the height of the light, but a buoy does not. See US Chart #1 for more details. Ref: CCME p 92-95
