USCG Navigation General Study Guide: Master Every Topic

Navigation General is the broadest module on the USCG license exam. Depending on which credential you're pursuing, the module ranges from 40 to 100 questions, covering everything from compass correction and tide tables to celestial sight reductions and GMDSS. It's the module that rewards structured study most — the material is predictable, the question types repeat, and a methodical candidate can approach it with a high degree of confidence.

This guide covers every major topic in the Navigation General module, roughly in the order you should learn them.

Compass Correction (Start Here)

Compass correction is the mechanical foundation of the navigation module. If you can't move confidently between true, magnetic, and compass bearings, everything downstream is harder.

The error chain: True → (apply Variation) → Magnetic → (apply Deviation) → Compass

Or remembering the mnemonic: True Virgins Make Dull Companions

• Variation is the angle between geographic north (true north) and magnetic north, read from the compass rose on the chart. It changes slowly over decades. West variation is subtracted when going from true to magnetic; east variation is added.
• Deviation is the compass error caused by the ship's own magnetic field. It's specific to each compass on each vessel, varies with vessel heading, and is recorded in a deviation table aboard the vessel.
• Compass error = variation + deviation combined

The exam will give you any two values and ask you to find the third, in both directions (true to compass, compass to true). Work these until the direction of the correction is automatic — the classic error is applying the correction in the wrong direction.

Compass bearings to true: add easterly errors, subtract westerly errors. (East is least, West is best — least = subtract, best = add... from compass to true.)

True to compass: reverse the operation.

Deviation Tables

You'll be given a deviation table — deviation by vessel's heading (per compass) — and asked to find the deviation for a specific heading. Tables are typically given in 15° or 45° increments and you'll need to interpolate.

Example: if the table shows deviation of 5°E at 090° per compass and 3°E at 135° per compass, the deviation at 112.5° per compass is 4°E (linear interpolation).

Tides and Tidal Currents

The USCG exam tests both the Tide Tables and the Tidal Current Tables (now merged into NOAA's digital predictions, but exam materials use the traditional tabular format).

Tide Table questions:

• Find the height of the water at a time between listed high/low water (interpolation using the Rule of Twelfths or the table of factors in the Tide Tables)
• Find the time of a given height of water
• Correction tables for secondary reference stations (apply time and height differences to the reference station)

The Rule of Twelfths is worth memorizing: in a 6-hour tidal cycle, the tide rises/falls 1/12 of its range in the first hour, 2/12 in the second, 3/12 in the third, 3/12 in the fourth, 2/12 in the fifth, 1/12 in the sixth.

Tidal Current Table questions:

• Find the velocity and direction of a tidal current at a given time between slack water and maximum current
• Set, drift, and how to correct course and speed for a tidal current

Current Sailing

Current sailing questions give you vessel speed and heading and ask you to find course made good (CMG) and speed made good (SMG) through the water accounting for a set and drift current.

The three vectors: vessel heading/speed through water + current set/drift = actual course/speed made good over ground.

These are drawn as vector diagrams. Practice drawing them consistently — vector problems done graphically are faster and less error-prone than pure arithmetic.

Running Fix and Cross-Bearing Fix

A cross-bearing fix uses simultaneous bearings on two or more charted objects to establish position. Draw each LOP (line of position) through the charted object at the observed bearing; intersection = position.

A running fix uses two bearings on the same object taken at different times, advancing the first LOP to the time of the second bearing by the DR track run between fixes. The exam tests both the concept and the calculation of advancing an LOP.

Distance off by angle on the bow: If you take two bearings on an object, note when it's 45° on the bow (relative bearing 045° or 315°) and again when it's 90° on the bow (abeam), the distance run between those two bearings equals your distance off the object when abeam. This is the classic "bow and beam bearing" or "four-point bearing" method.

Radar Plotting (ARPA)

Navigation General at the 100- and 200-ton level includes basic radar plotting:

• Own ship's speed and course
• Relative motion (RM) line of a target — where the target appears to be moving relative to your vessel
• True motion — the actual motion of the target over the ground
• CPA (closest point of approach) and TCPA (time to CPA) from the RM plot
• Determining whether a target is on a collision course (RM line pointing toward your vessel)

The exam gives you plotted information and asks you to read off the CPA or determine if a course change is needed.

Electronic Navigation

USCG exam questions on electronic navigation:

• GPS: How it works (time-distance from multiple satellites), types of error (satellite geometry, multipath, atmospheric delay), RAIM (Receiver Autonomous Integrity Monitoring), HDOP/PDOP
• DGPS: Differential correction, accuracy improvement, reference station concept
• AIS: What it broadcasts (MMSI, vessel name, course, speed, position), Class A vs. Class B transponders, when vessels are required to carry AIS (SOLAS vessels, U.S. requirements under 33 CFR 164.46)
• ECDIS: Required carriage under SOLAS for certain vessel classes, S-57 vector charts vs. raster charts, how to interpret chart updates and Notice to Mariners corrections

Celestial Navigation (200-Ton and Above)

For the Master 200 GT and higher, Navigation General connects with the celestial navigation module. Key concepts tested in Navigation General (as opposed to the full sight reduction in the celestial module):

• Time relationships: GMT, LMT, ZT (Zone Time), the relationship between longitude and time (15° = 1 hour)
• The concept of GHA (Greenwich Hour Angle) and LHA (Local Hour Angle)
• Latitude by meridian passage of the sun (noon sight): Latitude = 90° - Zenith Distance ± declination
• Latitude by Polaris: the altitude of Polaris corrected for its offset from the pole equals latitude at all times of year (corrections from the Nautical Almanac)

These appear in Navigation General as well as the dedicated celestial module at higher license levels.

GMDSS (Global Maritime Distress and Safety System)

At the 200-ton level especially, GMDSS concepts appear in the Navigation General module:

• Sea area definitions: A1 (within 20-30nm of a DSC shore station), A2 (out to ~400nm), A3 (global INMARSAT coverage, roughly ±70° latitude), A4 (polar regions)
• DSC (Digital Selective Calling): how to send a distress alert, the MMSI, the distress button procedure
• NAVTEX: automated MSI (Maritime Safety Information) broadcasts on 518 kHz
• EPIRBs: Category I (hydrostatic release, automatic), Category II (manual only), 406 MHz registration
• SARTs: Search and rescue transponders, radar detection on 9 GHz

How to Structure Your Navigation General Study

Week 1-2: Compass correction and deviation tables. Drill these daily until they're automatic.

Week 3: Tides and tidal currents — work through the Tide Table examples in the USCG exam prep questions.

Week 4: Current sailing vector diagrams. Draw them by hand.

Week 5: Running fix, cross-bearing, and distance-off calculations.

Week 6: Electronic navigation and GMDSS concepts.

Week 7-8: Celestial basics (if applicable to your license level) and practice full exam sections.

Week 9-10: Full timed practice exams. Target 80%+ before sitting.

The reference that covers this material most directly at exam depth is Dutton's Nautical Navigation (15th edition). Bowditch (American Practical Navigator, freely available from the NGA website) goes deeper on celestial and great circle sailing.

Practice with Binnacle School

Navigation General questions are predictable — the question bank is fixed and the topics repeat. [Binnacle School](/school) gives you timed practice sessions by topic category (compass correction, current sailing, radar plotting) so you can drill your weak areas efficiently.

The fastest candidates identify one or two categories where they consistently drop points and drill those specifically. Start your Navigation General practice →

Binnacle AI is not affiliated with the U.S. Coast Guard or the NMC. All exam topics reflect current NMC guidance as of 2026 — verify at uscg.mil/nmc. Not legal advice.