USNA Summer '20 Youngster Nav NN210 FINAL
EXAM Questions And Answers
DESCRIBE the terrestrial coordinate system; Correct Answers: A combination of latitude and
longitude is a position on the Earth's Grid.
Example:
Riverside Observatory coordinates:
- Lat. = 33°57' 12'' N
- Long. = 117°23' 46'' W
Remember:
1°= 60' (minutes)
1' = 60'' (seconds)
Latitude Correct Answers: - Equator is the reference for latitude;
- Measures angular distance north or south from the Equator (0º - 90º); and
- Described in degrees, minutes and seconds followed by the suffix N/S.
ᵠ = XXº XX' XX'' N/S
Longitude Correct Answers: Prime Meridian is the reference for longitude;
Measures the angular distance east or west from the Prime Meridian (0º - 180º); and
Described in degrees, minutes and seconds followed by the suffix E/W.
λ = XXXº XX' XX'' E/W
DEFINE chart projection; Correct Answers: Transforming spherical surface to a flat surface is called
projection. There are several hundred types, each with some particular property desirable for a
specific purpose; and
For NAV purposes, fall within 3 categories: plane, cylindrical or conic.
Mercator advantages Correct Answers: shape is distorted very little, direction is consistent, and map
is rectangular
Mercator disadvantages Correct Answers: 1) Inaccurate size & distance.
2) Distorted polar regions.
gnomonic advantages Correct Answers: Great Circles are represented by straight lines.
gnomic disadvantages Correct Answers: Distance and direction cannot be measured directly
(unusable as a working chart); and
, - Distortion of shape and scale increases as distance from the center of the projection (the point of
tangency) increases.
great circle Correct Answers: any circle formed on the surface of Earth by the intersection of a plane
passing through the center of the Earth, thereby dividing Earth into two equal parts.
Meridian - Great Circle that passes through the poles; and
Equator - Great Circle that is half-way from the poles.
small circle Correct Answers: One whose plane does not pass through the center of the earth
Parallel Correct Answers: Small Circle that is parallel to the Equator.
Rhumb Line Correct Answers: a line that crosses every meridian at the same angle. Helps to
navigate because a ship may maintain a true heading without change from starting point to
destination.
great circle routes Correct Answers: shortest distance between 2 points (follows a great circle). Not
practical to navigate because requires constant course changes.
National Ocean Service (NOS) Correct Answers: Governmental agency for charting the coastal
waters of US;
- Division of the National Oceanic & Atmospheric Admin;
- Charts are produced for coastal US waters, most rivers and Great Lakes for commercial and civilian
use.
Army Corps of Engineers are incharge of plotting what? Correct Answers: Mississippi River (and its
tributaries) and some inland lakes.
National Geospatial-Intelligence Agency (NGA) Correct Answers: - Nautical charts for the Department
of Defense and International use.
LIST the major information features of a nautical chart; Correct Answers: Publisher
Region identification
Main title
Projection and Scale
Datum
Depth and elevation notes
Cautionary notes
Tidal information
Datum Correct Answers: Reference point in which measurements are made and has important
implications when navigating with satellite-based systems. It must be taken into account to prevent
potential disaster.
Datum Shift Correct Answers: Difference between actual and plotted position when using different
datum (chart/chart or chart/GPS).
,DEFINE chart scale; Correct Answers: It's the ratio of a distance unit on the chart to the actual
distance on the surface of the Earth.
Ex.: Scale of 1:80,000 → means that one unit (inch, foot, meter, etc) on the chart represents 80,000
such units on the Earth.
Chart scale notes Correct Answers: Large Area = Small Scale
Small Scale = Large Area =less detail
Large Scale = small area = more detail
LIST the major categories of charts by scale; Correct Answers: Sailing (Smallest)
General
Coastal/ Approach
Harbor(Biggest)
EXPLAIN the importance of Chart One; Correct Answers: explains all the various ways that
information is represented on charts produced by the two agencies.
DEFINE line of position; Correct Answers: Whereas an exact position is a point on a chart, an LOP is
a line, along which the navigator knows he or she is located. It is measured from a NAVAID;
3 LOP for a reliable fix
Visual NAVAID Correct Answers: Fixed object used to obatin a visual LOP (bearing);
Object must be easy to identify visualy and marked on the nautical chart;
Buoys cannot be used to obtain a LOP ((they are not fixed)); and
Examples: towers, tanks, lights, piers, daymarkers.
RADAR NAVAID Correct Answers: Fixed objects and points of coast contour (easily identified on the
chart) are used to obatin a radar LOP (range); and
Matching object chosen from chart to the image on the radar is challenging;
Examples: lights, daymarkers, piers, bends on shore.
DEFINE fix; Correct Answers: A fix is a position of your vessel on the chart; and
It is obtained based on a combination of 3 lines of position or a set of coordinates (latitude and
longitude).
RECALL the LOP requirements for a fix and the symbols used in plotting; Correct Answers: Visual fix
is a Circle, where as a Radar Fix is a triangle. Need 3 LOP for a reliable fix
LIST the Navy's required fix intervals; Correct Answers: Restricted water: 3 minutes
Piloting Water:3-15 minutes
Coastal Water: 15-30 minutes
Open Ocean:30 minutes or as conditions warrant
DESCRIBE the optimal spread of visual LOPs; Correct Answers: Prevents the bearings from being
too close together and helps provide a more precise fix;
- The optimum spread for LOP's is 120°; and
, - If all NAVAIDs are on the same side of the ship, they should be 60° apart.
DEFINE dead reckoning. Correct Answers: The process of estimating your ship's future position
without considering the effects of wind and current. Based on the ship's ordered course and speed.
LIST the six rules of Dead Reckoning Correct Answers: 1..At least every hour on the hour while in
open ocean
2. At every course change
3. At every speed change
4. After every fix or running fix
5. When obtaining a single line of position (LOP)
6. Label each fix with course, speed, time, and draw a new course line from each fix or running fix.
The DR plot should cover at least the next two fix intervals.
MEMORIZE the speed/time/distance equation. Correct Answers: D = S x T
where: D = distance traveled in nautical miles (nm)
S = speed in knots
T = time in hours
Three Minute Rule Correct Answers: The distance of travel of a ship in yards in
three minutes is equal to its speed in knots multiplied by 100.
D = S x 100
where: D = distance traveled (yards)
S = speed (knots)
Six minute rule Correct Answers: The distance of travel of a ship in nautical miles in six minutes is
equal to its speed in knots divided by 10.
D = S / 10
where: D = distance traveled (NM) S = speed (knots)
DEFINE running fix. Correct Answers: A method for determining the ship's position with visual LOPs
when only one object is visible.
PLOT a running fix. Correct Answers: Take 3 LOPs from the object at 3 minute intervals, then
advance each LOP in parallel with the ordered course for predicted distance travelled (ie, 6 min for
the first LOP, 3 min for second LOP)
FIND corrections for a given chart. Correct Answers: K40 = chapter + line in chart one
EXAM Questions And Answers
DESCRIBE the terrestrial coordinate system; Correct Answers: A combination of latitude and
longitude is a position on the Earth's Grid.
Example:
Riverside Observatory coordinates:
- Lat. = 33°57' 12'' N
- Long. = 117°23' 46'' W
Remember:
1°= 60' (minutes)
1' = 60'' (seconds)
Latitude Correct Answers: - Equator is the reference for latitude;
- Measures angular distance north or south from the Equator (0º - 90º); and
- Described in degrees, minutes and seconds followed by the suffix N/S.
ᵠ = XXº XX' XX'' N/S
Longitude Correct Answers: Prime Meridian is the reference for longitude;
Measures the angular distance east or west from the Prime Meridian (0º - 180º); and
Described in degrees, minutes and seconds followed by the suffix E/W.
λ = XXXº XX' XX'' E/W
DEFINE chart projection; Correct Answers: Transforming spherical surface to a flat surface is called
projection. There are several hundred types, each with some particular property desirable for a
specific purpose; and
For NAV purposes, fall within 3 categories: plane, cylindrical or conic.
Mercator advantages Correct Answers: shape is distorted very little, direction is consistent, and map
is rectangular
Mercator disadvantages Correct Answers: 1) Inaccurate size & distance.
2) Distorted polar regions.
gnomonic advantages Correct Answers: Great Circles are represented by straight lines.
gnomic disadvantages Correct Answers: Distance and direction cannot be measured directly
(unusable as a working chart); and
, - Distortion of shape and scale increases as distance from the center of the projection (the point of
tangency) increases.
great circle Correct Answers: any circle formed on the surface of Earth by the intersection of a plane
passing through the center of the Earth, thereby dividing Earth into two equal parts.
Meridian - Great Circle that passes through the poles; and
Equator - Great Circle that is half-way from the poles.
small circle Correct Answers: One whose plane does not pass through the center of the earth
Parallel Correct Answers: Small Circle that is parallel to the Equator.
Rhumb Line Correct Answers: a line that crosses every meridian at the same angle. Helps to
navigate because a ship may maintain a true heading without change from starting point to
destination.
great circle routes Correct Answers: shortest distance between 2 points (follows a great circle). Not
practical to navigate because requires constant course changes.
National Ocean Service (NOS) Correct Answers: Governmental agency for charting the coastal
waters of US;
- Division of the National Oceanic & Atmospheric Admin;
- Charts are produced for coastal US waters, most rivers and Great Lakes for commercial and civilian
use.
Army Corps of Engineers are incharge of plotting what? Correct Answers: Mississippi River (and its
tributaries) and some inland lakes.
National Geospatial-Intelligence Agency (NGA) Correct Answers: - Nautical charts for the Department
of Defense and International use.
LIST the major information features of a nautical chart; Correct Answers: Publisher
Region identification
Main title
Projection and Scale
Datum
Depth and elevation notes
Cautionary notes
Tidal information
Datum Correct Answers: Reference point in which measurements are made and has important
implications when navigating with satellite-based systems. It must be taken into account to prevent
potential disaster.
Datum Shift Correct Answers: Difference between actual and plotted position when using different
datum (chart/chart or chart/GPS).
,DEFINE chart scale; Correct Answers: It's the ratio of a distance unit on the chart to the actual
distance on the surface of the Earth.
Ex.: Scale of 1:80,000 → means that one unit (inch, foot, meter, etc) on the chart represents 80,000
such units on the Earth.
Chart scale notes Correct Answers: Large Area = Small Scale
Small Scale = Large Area =less detail
Large Scale = small area = more detail
LIST the major categories of charts by scale; Correct Answers: Sailing (Smallest)
General
Coastal/ Approach
Harbor(Biggest)
EXPLAIN the importance of Chart One; Correct Answers: explains all the various ways that
information is represented on charts produced by the two agencies.
DEFINE line of position; Correct Answers: Whereas an exact position is a point on a chart, an LOP is
a line, along which the navigator knows he or she is located. It is measured from a NAVAID;
3 LOP for a reliable fix
Visual NAVAID Correct Answers: Fixed object used to obatin a visual LOP (bearing);
Object must be easy to identify visualy and marked on the nautical chart;
Buoys cannot be used to obtain a LOP ((they are not fixed)); and
Examples: towers, tanks, lights, piers, daymarkers.
RADAR NAVAID Correct Answers: Fixed objects and points of coast contour (easily identified on the
chart) are used to obatin a radar LOP (range); and
Matching object chosen from chart to the image on the radar is challenging;
Examples: lights, daymarkers, piers, bends on shore.
DEFINE fix; Correct Answers: A fix is a position of your vessel on the chart; and
It is obtained based on a combination of 3 lines of position or a set of coordinates (latitude and
longitude).
RECALL the LOP requirements for a fix and the symbols used in plotting; Correct Answers: Visual fix
is a Circle, where as a Radar Fix is a triangle. Need 3 LOP for a reliable fix
LIST the Navy's required fix intervals; Correct Answers: Restricted water: 3 minutes
Piloting Water:3-15 minutes
Coastal Water: 15-30 minutes
Open Ocean:30 minutes or as conditions warrant
DESCRIBE the optimal spread of visual LOPs; Correct Answers: Prevents the bearings from being
too close together and helps provide a more precise fix;
- The optimum spread for LOP's is 120°; and
, - If all NAVAIDs are on the same side of the ship, they should be 60° apart.
DEFINE dead reckoning. Correct Answers: The process of estimating your ship's future position
without considering the effects of wind and current. Based on the ship's ordered course and speed.
LIST the six rules of Dead Reckoning Correct Answers: 1..At least every hour on the hour while in
open ocean
2. At every course change
3. At every speed change
4. After every fix or running fix
5. When obtaining a single line of position (LOP)
6. Label each fix with course, speed, time, and draw a new course line from each fix or running fix.
The DR plot should cover at least the next two fix intervals.
MEMORIZE the speed/time/distance equation. Correct Answers: D = S x T
where: D = distance traveled in nautical miles (nm)
S = speed in knots
T = time in hours
Three Minute Rule Correct Answers: The distance of travel of a ship in yards in
three minutes is equal to its speed in knots multiplied by 100.
D = S x 100
where: D = distance traveled (yards)
S = speed (knots)
Six minute rule Correct Answers: The distance of travel of a ship in nautical miles in six minutes is
equal to its speed in knots divided by 10.
D = S / 10
where: D = distance traveled (NM) S = speed (knots)
DEFINE running fix. Correct Answers: A method for determining the ship's position with visual LOPs
when only one object is visible.
PLOT a running fix. Correct Answers: Take 3 LOPs from the object at 3 minute intervals, then
advance each LOP in parallel with the ordered course for predicted distance travelled (ie, 6 min for
the first LOP, 3 min for second LOP)
FIND corrections for a given chart. Correct Answers: K40 = chapter + line in chart one
