ASA 105 Coastal Navigation
Certification Exam Study Guide
(2025–2026 Edition): Essential
Questions & Answers with Detailed
Rationales, Chart-Based Explanations,
and Verified Solutions for Guaranteed
Exam Success
Question: What is the alternate name for latitude?
Answer: Parallels.
Rationale: Lines of latitude run parallel to the equator and to each other,
hence the name "parallels".
Question: How many degrees north is the North Pole?
Answer: 90 degrees north latitude.
Rationale: Latitude is measured from the equator (0°) to the poles (90°
north or south).
Question: How many degrees south is the South Pole?
Answer: 90 degrees south latitude.
Rationale: The South Pole is located at the maximum southern latitude.
Question: One degree of latitude equals how many minutes?
Answer: 60 minutes.
Rationale: Each degree of latitude is subdivided into 60 minutes of arc.
,Question: What is one nautical mile equal to in terms of latitude?
Answer: 1 minute of latitude.
Rationale: This is the fundamental definition of the nautical mile, making it
convenient for measuring distance on charts.
Question: What is the International Date Line?
Answer: 180 degrees longitude.
Rationale: This meridian marks the change of calendar day when crossing
it.
Question: Is longitude ever used to measure distance?
Answer: No.
Rationale: Lines of longitude converge at the poles, so the distance
represented by one minute of longitude varies with latitude. Only latitude is
used for distance measurement.
Question: On a compass rose, what do the outer and inner rings represent?
Answer: The outer ring represents True North (Geographic); the inner ring
represents Magnetic North.
Rationale: The difference between the two is variation, which must be
applied when converting between true and magnetic directions.
Question: What is the mnemonic for converting between True, Magnetic,
and Compass?
Answer: TVMDC (True, Variation, Magnetic, Deviation, Compass).
Rationale: This mnemonic helps remember the order of correction when
going from True to Compass or vice versa.
Question: A vessel is steering a compass course of 135° C. Variation is 12°
W and deviation is 3° E. What is the true course?
Answer: 126° T.
Rationale: Convert Compass to True: C + Dev(E) + Var(W) = T. 135 + 3 +
(−12) = 126° T.
, Question: You are steering a true course of 270° T. Variation is 15° W and
deviation is 2° E. What compass course should you steer?
Answer: 253° C.
Rationale: Apply TVMDC in reverse: T − Var(W) = M (270 − 15 = 255° M),
then M − Dev(E) = C (255 − 2 = 253° C).
Question: The bearing to a lighthouse is 045° T. What type of bearing is
this?
Answer: True bearing.
Rationale: A bearing referenced to True North is a true bearing. Relative
bearing is measured from the vessel's heading, while magnetic and
compass bearings are referenced to magnetic and compass north
respectively.
Aids to Navigation (ATON)
Question: What color and shape are markers on the starboard side of a
channel when returning from seaward in U.S. waters?
Answer: Red, cone/triangle shaped, with even numbers.
Rationale: The mnemonic "Red, Right, Returning" reminds mariners that
red markers are kept to the right (starboard) when returning to port.
Question: What color and shape are markers on the port side of a channel
when returning from seaward in U.S. waters?
Answer: Green, cylindrical/square (can), with odd numbers.
Rationale: Green cans mark the left (port) side of the channel when
returning from seaward.
Question: What is a Safe Water buoy?
Answer: A red and white vertically striped buoy marking a fairway or mid-
channel.
Certification Exam Study Guide
(2025–2026 Edition): Essential
Questions & Answers with Detailed
Rationales, Chart-Based Explanations,
and Verified Solutions for Guaranteed
Exam Success
Question: What is the alternate name for latitude?
Answer: Parallels.
Rationale: Lines of latitude run parallel to the equator and to each other,
hence the name "parallels".
Question: How many degrees north is the North Pole?
Answer: 90 degrees north latitude.
Rationale: Latitude is measured from the equator (0°) to the poles (90°
north or south).
Question: How many degrees south is the South Pole?
Answer: 90 degrees south latitude.
Rationale: The South Pole is located at the maximum southern latitude.
Question: One degree of latitude equals how many minutes?
Answer: 60 minutes.
Rationale: Each degree of latitude is subdivided into 60 minutes of arc.
,Question: What is one nautical mile equal to in terms of latitude?
Answer: 1 minute of latitude.
Rationale: This is the fundamental definition of the nautical mile, making it
convenient for measuring distance on charts.
Question: What is the International Date Line?
Answer: 180 degrees longitude.
Rationale: This meridian marks the change of calendar day when crossing
it.
Question: Is longitude ever used to measure distance?
Answer: No.
Rationale: Lines of longitude converge at the poles, so the distance
represented by one minute of longitude varies with latitude. Only latitude is
used for distance measurement.
Question: On a compass rose, what do the outer and inner rings represent?
Answer: The outer ring represents True North (Geographic); the inner ring
represents Magnetic North.
Rationale: The difference between the two is variation, which must be
applied when converting between true and magnetic directions.
Question: What is the mnemonic for converting between True, Magnetic,
and Compass?
Answer: TVMDC (True, Variation, Magnetic, Deviation, Compass).
Rationale: This mnemonic helps remember the order of correction when
going from True to Compass or vice versa.
Question: A vessel is steering a compass course of 135° C. Variation is 12°
W and deviation is 3° E. What is the true course?
Answer: 126° T.
Rationale: Convert Compass to True: C + Dev(E) + Var(W) = T. 135 + 3 +
(−12) = 126° T.
, Question: You are steering a true course of 270° T. Variation is 15° W and
deviation is 2° E. What compass course should you steer?
Answer: 253° C.
Rationale: Apply TVMDC in reverse: T − Var(W) = M (270 − 15 = 255° M),
then M − Dev(E) = C (255 − 2 = 253° C).
Question: The bearing to a lighthouse is 045° T. What type of bearing is
this?
Answer: True bearing.
Rationale: A bearing referenced to True North is a true bearing. Relative
bearing is measured from the vessel's heading, while magnetic and
compass bearings are referenced to magnetic and compass north
respectively.
Aids to Navigation (ATON)
Question: What color and shape are markers on the starboard side of a
channel when returning from seaward in U.S. waters?
Answer: Red, cone/triangle shaped, with even numbers.
Rationale: The mnemonic "Red, Right, Returning" reminds mariners that
red markers are kept to the right (starboard) when returning to port.
Question: What color and shape are markers on the port side of a channel
when returning from seaward in U.S. waters?
Answer: Green, cylindrical/square (can), with odd numbers.
Rationale: Green cans mark the left (port) side of the channel when
returning from seaward.
Question: What is a Safe Water buoy?
Answer: A red and white vertically striped buoy marking a fairway or mid-
channel.
