ASA 105 EXAM V2 2026/2027 | Coastal Navigation
Certification | Verified Q&A | Pass Guaranteed - A+ Graded
SECTION 1: NAUTICAL CHARTS & CHART PROJECTIONS (20
QUESTIONS)
Q1: On a Mercator projection chart, a rhumb line appears as a straight line. Which
statement accurately describes the geometric property of a rhumb line?
A. It is the shortest distance between two points on the Earth's surface
B. It crosses all meridians at the same angle [CORRECT]
C. It follows the curvature of the Earth as a great circle
D. It is only usable for distances less than 10 nautical miles
Correct Answer: B
Rationale: A rhumb line is a path of constant bearing that crosses each meridian at the
same angle, which is why it plots as a straight line on a Mercator chart. A great circle is
the shortest distance between two points on the Earth's surface, not a rhumb line.
Mercator charts are designed specifically so that rhumb lines are straight for ease of
navigation, though they are not the shortest path for long distances.
Q2: A navigator measures a distance of 3 nautical miles using the latitude scale on the
left side of a Mercator chart. Which statement explains why this measurement is
accurate?
A. The latitude scale is compressed near the equator and expanded near the poles
B. One minute of latitude always equals one nautical mile regardless of latitude
[CORRECT]
C. The longitude scale is identical to the latitude scale at all latitudes
D. Distance must always be measured using the longitude scale for accuracy
Correct Answer: B
Rationale: One minute of latitude equals one nautical mile (6,076 feet) everywhere on
Earth because latitude is defined by angular distance from the equator. The latitude
scale on a Mercator chart is therefore the correct scale for measuring distance. The
,longitude scale varies with latitude (compressed near the poles), so it must never be
used for distance measurement. The latitude scale does expand toward the poles on a
Mercator chart, but each minute still represents one nautical mile.
Q3: A chart labeled as "1:80,000 scale" is considered which type of chart, and what does
this representative fraction indicate?
A. A small-scale chart where 1 unit on the chart equals 80,000 units on the Earth
[CORRECT]
B. A large-scale chart where 1 inch equals 80,000 inches in reality
C. A harbor chart where 1 centimeter equals 800 meters on the Earth
D. A general chart where 1 nautical mile is represented by 80,000 inches
Correct Answer: A
Rationale: A scale of 1:80,000 means one unit of measurement on the chart represents
80,000 of the same units on the Earth's surface. This is classified as a small-scale chart
(coastal chart), as large-scale charts typically have ratios of 1:20,000 or larger for
harbor detail. The representative fraction is unit-independent and applies equally to any
unit of measurement.
Q4: A navigator needs to determine the exact meaning of a chart symbol representing a
submerged rock. Which publication provides the standardized key to all U.S. nautical
chart symbols and abbreviations?
A. The U.S. Coast Pilot
B. Chart No. 1: Nautical Chart Symbols and Abbreviations [CORRECT]
C. The Notice to Mariners
D. The American Practical Navigator (Bowditch)
Correct Answer: B
Rationale: Chart No. 1 is the official publication that provides a complete graphic key to
all symbols, abbreviations, and terms used on U.S. nautical charts and NOAA ENC
symbols. The Coast Pilot provides coastal descriptions and sailing directions, the
Notice to Mariners provides chart corrections, and Bowditch is a comprehensive
navigation reference but not the symbol key.
Q5: A vessel is navigating using an Electronic Navigational Chart (ENC). Which
characteristic distinguishes an ENC from a Raster Navigational Chart (RNC)?
,A. An ENC is a scanned image of a paper chart while an RNC is a vector database
B. An ENC is a vector database that can be queried for underlying object data
[CORRECT]
C. An ENC requires continuous GPS input while an RNC does not
D. An RNC provides real-time tide data while an ENC does not
Correct Answer: B
Rationale: An ENC is a vector-format digital chart database conforming to International
Hydrographic Organization (IHO) S-57/S-101 standards, where each chart feature is a
data object that can be queried for underlying information (depth, light characteristics,
etc.). An RNC is simply a geo-referenced scanned image of a paper chart without
underlying object data. Both require position input for overlay, and neither provides
real-time tide data inherently.
Q6: A navigator measures depth soundings on a U.S. coastal chart and notes that all
depths are referenced to Mean Lower Low Water (MLLW). If the tide tables predict a
high tide of 8.5 feet above MLLW, what is the total water depth at a charted sounding of
12 feet?
A. 8.5 feet
B. 12.0 feet
C. 20.5 feet [CORRECT]
D. 3.5 feet
Correct Answer: C
Rationale: The total water depth equals the charted sounding (depth referenced to the
chart datum, MLLW) plus the height of tide above that datum. Therefore, 12 feet + 8.5
feet = 20.5 feet of actual water under the keel at high tide. Subtracting tide from charted
depth would give an incorrect and dangerously shallow value.
Q7: A navigator is updating charts using the Local Notice to Mariners. Which statement
accurately describes the purpose of this publication?
A. It provides daily weather forecasts for coastal waters
B. It contains corrections to nautical charts, Coast Pilots, and Light Lists issued weekly
by the U.S. Coast Guard [CORRECT]
C. It replaces the need for annual chart purchases
D. It lists only temporary changes to aids to navigation
Correct Answer: B
, Rationale: The Local Notice to Mariners is published weekly by each U.S. Coast Guard
District and contains information necessary to update nautical charts, Coast Pilots,
Light Lists, and other navigational publications. It includes permanent changes,
temporary changes, and advance notice of important changes. Mariners are legally
required to keep charts and publications corrected for safety.
Q8: On a Mercator chart, the navigator notices that the spacing between lines of
longitude increases toward the poles. Which geometric consequence results from this
distortion?
A. Great circles plot as straight lines
B. The scale of distance increases with latitude [CORRECT]
C. Areas near the poles are shown smaller than they actually are
D. Rhumb lines become curved lines near the poles
Correct Answer: B
Rationale: The Mercator projection is a cylindrical projection where the cylinder is
tangent at the equator. To maintain the property that rhumb lines are straight and
angles are true, the distance between parallels of latitude increases toward the poles.
This means the scale of the chart expands with latitude, so distance must always be
measured from the latitude scale near the area of interest. Great circles appear curved
(except the equator and meridians), and polar areas are greatly enlarged, not reduced.
Q9: A navigator is plotting a position using GPS coordinates referenced to the WGS 84
datum. The nautical chart in use is referenced to NAD 83. Which action is most
appropriate?
A. Convert all GPS coordinates to NAD 27 before plotting
B. Apply a datum shift correction, though WGS 84 and NAD 83 differ by less than 2
meters in most areas [CORRECT]
C. Ignore the difference because all datums are equivalent for coastal navigation
D. Use only the chart's compass rose for coordinate conversion
Correct Answer: B
Rationale: WGS 84 (World Geodetic System 1984) and NAD 83 (North American Datum
1983) are both earth-centered datums that differ by less than 2 meters in most
locations, which is negligible for coastal navigation. However, using WGS 84
coordinates on a NAD 27 chart (older charts) could produce errors of hundreds of
Certification | Verified Q&A | Pass Guaranteed - A+ Graded
SECTION 1: NAUTICAL CHARTS & CHART PROJECTIONS (20
QUESTIONS)
Q1: On a Mercator projection chart, a rhumb line appears as a straight line. Which
statement accurately describes the geometric property of a rhumb line?
A. It is the shortest distance between two points on the Earth's surface
B. It crosses all meridians at the same angle [CORRECT]
C. It follows the curvature of the Earth as a great circle
D. It is only usable for distances less than 10 nautical miles
Correct Answer: B
Rationale: A rhumb line is a path of constant bearing that crosses each meridian at the
same angle, which is why it plots as a straight line on a Mercator chart. A great circle is
the shortest distance between two points on the Earth's surface, not a rhumb line.
Mercator charts are designed specifically so that rhumb lines are straight for ease of
navigation, though they are not the shortest path for long distances.
Q2: A navigator measures a distance of 3 nautical miles using the latitude scale on the
left side of a Mercator chart. Which statement explains why this measurement is
accurate?
A. The latitude scale is compressed near the equator and expanded near the poles
B. One minute of latitude always equals one nautical mile regardless of latitude
[CORRECT]
C. The longitude scale is identical to the latitude scale at all latitudes
D. Distance must always be measured using the longitude scale for accuracy
Correct Answer: B
Rationale: One minute of latitude equals one nautical mile (6,076 feet) everywhere on
Earth because latitude is defined by angular distance from the equator. The latitude
scale on a Mercator chart is therefore the correct scale for measuring distance. The
,longitude scale varies with latitude (compressed near the poles), so it must never be
used for distance measurement. The latitude scale does expand toward the poles on a
Mercator chart, but each minute still represents one nautical mile.
Q3: A chart labeled as "1:80,000 scale" is considered which type of chart, and what does
this representative fraction indicate?
A. A small-scale chart where 1 unit on the chart equals 80,000 units on the Earth
[CORRECT]
B. A large-scale chart where 1 inch equals 80,000 inches in reality
C. A harbor chart where 1 centimeter equals 800 meters on the Earth
D. A general chart where 1 nautical mile is represented by 80,000 inches
Correct Answer: A
Rationale: A scale of 1:80,000 means one unit of measurement on the chart represents
80,000 of the same units on the Earth's surface. This is classified as a small-scale chart
(coastal chart), as large-scale charts typically have ratios of 1:20,000 or larger for
harbor detail. The representative fraction is unit-independent and applies equally to any
unit of measurement.
Q4: A navigator needs to determine the exact meaning of a chart symbol representing a
submerged rock. Which publication provides the standardized key to all U.S. nautical
chart symbols and abbreviations?
A. The U.S. Coast Pilot
B. Chart No. 1: Nautical Chart Symbols and Abbreviations [CORRECT]
C. The Notice to Mariners
D. The American Practical Navigator (Bowditch)
Correct Answer: B
Rationale: Chart No. 1 is the official publication that provides a complete graphic key to
all symbols, abbreviations, and terms used on U.S. nautical charts and NOAA ENC
symbols. The Coast Pilot provides coastal descriptions and sailing directions, the
Notice to Mariners provides chart corrections, and Bowditch is a comprehensive
navigation reference but not the symbol key.
Q5: A vessel is navigating using an Electronic Navigational Chart (ENC). Which
characteristic distinguishes an ENC from a Raster Navigational Chart (RNC)?
,A. An ENC is a scanned image of a paper chart while an RNC is a vector database
B. An ENC is a vector database that can be queried for underlying object data
[CORRECT]
C. An ENC requires continuous GPS input while an RNC does not
D. An RNC provides real-time tide data while an ENC does not
Correct Answer: B
Rationale: An ENC is a vector-format digital chart database conforming to International
Hydrographic Organization (IHO) S-57/S-101 standards, where each chart feature is a
data object that can be queried for underlying information (depth, light characteristics,
etc.). An RNC is simply a geo-referenced scanned image of a paper chart without
underlying object data. Both require position input for overlay, and neither provides
real-time tide data inherently.
Q6: A navigator measures depth soundings on a U.S. coastal chart and notes that all
depths are referenced to Mean Lower Low Water (MLLW). If the tide tables predict a
high tide of 8.5 feet above MLLW, what is the total water depth at a charted sounding of
12 feet?
A. 8.5 feet
B. 12.0 feet
C. 20.5 feet [CORRECT]
D. 3.5 feet
Correct Answer: C
Rationale: The total water depth equals the charted sounding (depth referenced to the
chart datum, MLLW) plus the height of tide above that datum. Therefore, 12 feet + 8.5
feet = 20.5 feet of actual water under the keel at high tide. Subtracting tide from charted
depth would give an incorrect and dangerously shallow value.
Q7: A navigator is updating charts using the Local Notice to Mariners. Which statement
accurately describes the purpose of this publication?
A. It provides daily weather forecasts for coastal waters
B. It contains corrections to nautical charts, Coast Pilots, and Light Lists issued weekly
by the U.S. Coast Guard [CORRECT]
C. It replaces the need for annual chart purchases
D. It lists only temporary changes to aids to navigation
Correct Answer: B
, Rationale: The Local Notice to Mariners is published weekly by each U.S. Coast Guard
District and contains information necessary to update nautical charts, Coast Pilots,
Light Lists, and other navigational publications. It includes permanent changes,
temporary changes, and advance notice of important changes. Mariners are legally
required to keep charts and publications corrected for safety.
Q8: On a Mercator chart, the navigator notices that the spacing between lines of
longitude increases toward the poles. Which geometric consequence results from this
distortion?
A. Great circles plot as straight lines
B. The scale of distance increases with latitude [CORRECT]
C. Areas near the poles are shown smaller than they actually are
D. Rhumb lines become curved lines near the poles
Correct Answer: B
Rationale: The Mercator projection is a cylindrical projection where the cylinder is
tangent at the equator. To maintain the property that rhumb lines are straight and
angles are true, the distance between parallels of latitude increases toward the poles.
This means the scale of the chart expands with latitude, so distance must always be
measured from the latitude scale near the area of interest. Great circles appear curved
(except the equator and meridians), and polar areas are greatly enlarged, not reduced.
Q9: A navigator is plotting a position using GPS coordinates referenced to the WGS 84
datum. The nautical chart in use is referenced to NAD 83. Which action is most
appropriate?
A. Convert all GPS coordinates to NAD 27 before plotting
B. Apply a datum shift correction, though WGS 84 and NAD 83 differ by less than 2
meters in most areas [CORRECT]
C. Ignore the difference because all datums are equivalent for coastal navigation
D. Use only the chart's compass rose for coordinate conversion
Correct Answer: B
Rationale: WGS 84 (World Geodetic System 1984) and NAD 83 (North American Datum
1983) are both earth-centered datums that differ by less than 2 meters in most
locations, which is negligible for coastal navigation. However, using WGS 84
coordinates on a NAD 27 chart (older charts) could produce errors of hundreds of
