- What the Letters Point To
- Decoding the Credential: Master, Under 100 GRT, Great Lakes and Inland
- Who Governs It: The National Maritime Center
- The Five Preparation Groups at a Glance
- Rules of the Road: Q100 or Q300 Depending on Your Route
- Deck General (Q347) and Deck Safety (Q348)
- Navigation General (Q349) and Chart Plot (Q350)
- Q352: The Raise-of-Grade Module You Should Not Confuse With a Sixth Group
- Great Lakes and Inland Versus Inland Only
- Why Your Approval to Test Controls Everything
- Sequencing Your Preparation
- Frequently Asked Questions
- NM1GI here means National Master 100 GL and Inland, a U.S. Coast Guard mariner credential for vessels under 100 GRT.
- The governing body is the U.S. Coast Guard National Maritime Center, not a private certification organization.
- Preparation breaks into five route-aware groups: Rules, Deck General, Deck Safety, Navigation General, and Chart Plot.
- Your individual NMC approval to test, not a generic outline, determines your assigned modules and any credit.
What the Letters Point To
If you searched for what NM1GI stands for, the short answer on this site is National Master 100 GL and Inland. It refers to a U.S. Coast Guard mariner credential: Master (or Mate) of vessels of less than 100 gross register tons, with Great Lakes and Inland waters as the route. The Coast Guard's own exam listing for this credential is catalogued as GLI06, "Master or Mate less than 100 GRT."
The acronym is a compact label, so it helps to unpack every piece of it. Each fragment tells you something concrete about what the credential covers and what you will be tested on. If you are comparing this to other credentials that happen to share similar-looking letters, set those aside: everything below is specific to the National Master 100 GL and Inland credential and the Coast Guard process behind it.
For related definitions, you can also browse What Is NM1GI?, NM1GI Meaning, and What Is NM1GI Certification?, which approach the same question from slightly different angles.
Decoding the Credential: Master, Under 100 GRT, Great Lakes and Inland
Break the name into its working parts:
- National: This is a U.S. credential issued under Coast Guard authority, not an international or voluntary industry certificate.
- Master: The credential identity is Master, the officer in command of the vessel. The exam listing groups Master and Mate for vessels under 100 GRT, but the identity you are preparing around here is Master.
- 100: The tonnage ceiling. The credential applies to vessels of less than 100 gross register tons (GRT).
- GL and Inland: The route. Great Lakes and Inland waters, as distinct from an Inland-only route. This distinction changes parts of what you must study, which is covered in a later section.
If you want the formal requirements side of the story, see NM1GI Requirements: Eligibility, Prerequisites & How to Qualify. This article stays focused on what the name means and what it implies about the examination.
Who Governs It: The National Maritime Center
The governing body is the United States Coast Guard National Maritime Center (NMC). That fact shapes everything about how this credential works. Unlike a vendor certification with a commercial testing network and a published pass-rate dashboard, a Coast Guard credential runs through federal regulation, official examination guides, and an individual approval process.
A few practical consequences follow:
- The authoritative references are NMC publications: the exam listing for GLI06 and the NMC examination guide.
- The NMC examination guide referenced for this material reflects regulations effective March 24, 2014. It should be used alongside the current published NMC module-topic index and your individual approval to test, not treated as a brand-new universal exam specification.
- Official percentage weights for the topic areas are not published in the materials this site relies on. Any source claiming exact percentages for each group should be treated with skepticism.
Because of that last point, this site describes the exam content as unweighted, route-aware preparation groups rather than a single mandatory exam with fixed weightings. If you want to understand how scoring and thresholds are framed, read NM1GI Passing Score: Exactly What You Need to Pass.
The Five Preparation Groups at a Glance
The NMC lists the modules for this credential, and for study purposes they sort into five full-route preparation groups. The route-specific Rules choice counts once, so you are not preparing two Rules subjects.
| Group | Module | What it covers (headline topics) |
|---|---|---|
| 1 | Rules of the Road: International and Inland (Q100) or Inland (Q300), per approved route | Watchkeeping; COLREGS; Inland Navigational Rules |
| 2 | Deck General (Q347) | Seamanship, vessel handling, anchoring, heavy weather, maritime law, ship's business |
| 3 | Deck Safety (Q348) | Stability, firefighting, emergency procedures, communications and signals |
| 4 | Navigation General: Great Lakes and Inland (Q349) | Position determination, charts, compasses, meteorology, tides and currents |
| 5 | Navigation Problems: Chart Plot (Q350) | Piloting, distance off, bearings, fixes, dead reckoning, electronic navigation |
For a deeper walk through each area, the companion piece NM1GI Exam Domains: Complete Guide to All 5 Content Areas goes domain by domain.
Rules of the Road: Q100 or Q300 Depending on Your Route
Domain 1: Rules of the Road (Q100 or Q300)
This is the one group where your approved route changes which module you sit. Candidates approved for the broader route take International and Inland (Q100); those approved for Inland only take Inland (Q300). Either way, it is a single Rules subject.
- Watchkeeping: the lookout, safe speed, and bridge-watch responsibilities embedded in the rules.
- COLREGS: the International Regulations for Preventing Collisions at Sea, relevant when your route calls for them.
- Inland Navigational Rules: the rules that govern inland waters and the Great Lakes, with their own signals and situations.
Do not treat the two rule sets as interchangeable. Where your approval specifies one, study that one thoroughly and treat the other as supporting context only if your approval calls for it.
Deck General (Q347) and Deck Safety (Q348)
These two modules form the seamanship backbone of the credential, and they contain most of the "judgment" content: the material where you must reason about a vessel in a situation rather than recall a single fact.
Domain 2: Deck General (Q347)
The published topic list is broad and practical. It spans hands-on seamanship, vessel handling, law, and shipboard management.
- Seamanship and marlinspike: knots, splices, and rope work; purchases, blocks, and tackle.
- Vessel maneuvering and handling: handling in rivers and estuaries, maneuvering in shallow water, interaction with a bank or passing ship, berthing and unberthing, and anchoring and mooring, including dragging anchors and clearing fouled anchors.
- Handling concepts: turn circle, pivot point, advance and transfer, and wake reduction.
- Heavy weather operations: including maneuvering for launching lifeboats and liferafts in heavy weather (a Great Lakes-specific item, discussed below).
- Maritime law and administration: national maritime law, credentialing of seamen, shipboard management and training, ship sanitation, vessel alteration/repair/hot work, ship's business, and certificates and documents required.
Domain 3: Deck Safety (Q348)
This module concentrates on keeping the vessel and everyone aboard alive when something goes wrong.
- Stability, construction, and damage control: principles of vessel construction, and trim and stability.
- Vessel power plants: small engine operations and maintenance.
- Fire: prevention and firefighting appliances, organization of fire drills, classes and chemistry of fire, firefighting systems, and basic firefighting and prevention.
- Emergency procedures: collision, temporary repairs, passenger and crew safety in emergencies, fire or explosion, abandon ship procedures, rescuing survivors from a ship or aircraft in distress, man overboard procedures, and emergency towing.
- Communications and signals: storm, wreck, distress, and special signals.
Navigation General (Q349) and Chart Plot (Q350)
The last two groups are navigation, and they overlap in subject matter but differ in how you demonstrate it.
Domain 4: Navigation General: Great Lakes and Inland (Q349)
This is the knowledge side of navigation: concepts, instruments, publications, and environmental factors.
- Navigation and position determination: piloting, distance off, bearing problems, fix or running fix, chart navigation, dead reckoning, electronic navigation, and instruments and accessories.
- Charts and publications: aids to navigation, charts, navigation publications, and Notices to Mariners.
- Compasses: magnetic and gyro principles, magnetic compass error and correction, determination of compass error, and terrestrial observation.
- Meteorology and oceanography: characteristics of weather systems, weather charts and reports, and tides and tidal currents.
Domain 5: Navigation Problems: Chart Plot (Q350)
This is the applied side. The listed topics echo piloting, distance off, bearing problems, fix or running fix, chart navigation, dead reckoning, electronic navigation, instruments and accessories, aids to navigation, and charts, publications, and notices.
- Chart plotting (Q350) is a retained, distinct skill set: you work problems on a chart rather than answering concept questions.
- Accuracy with plotting tools and consistent method matter more than speed of recall.
Candidates who are strong on theory but rusty on plotting are a common profile. For a frank view of where people struggle, see How Hard Is the NM1GI Exam? Complete Difficulty Guide.
Q352: The Raise-of-Grade Module You Should Not Confuse With a Sixth Group
Q352, Navigation and Deck General/Safety, appears in the NMC's listing as a separately listed raise-of-grade route module. It is easy to misread, so be precise about what it is and is not:
- It is not a universal sixth group appended to the five full-original preparation groups.
- It is not a second Rules subject.
- It is a route-specific module that may apply depending on the path assigned to you.
Key Takeaway
Count five groups for a full-original preparation plan, with Rules counted once. Treat Q352 as applicable only if your approval to test assigns it. Never budget study time for it by default.
Great Lakes and Inland Versus Inland Only
The "GL and Inland" in the name is not decoration. The NMC's topic table marks certain items with a footnote identifying them as Great Lakes-specific. The two called out in the materials this article relies on are:
- Heavy weather operations (Deck General), and
- Maneuvering for launching of lifeboats and liferafts in heavy weather (Deck General).
If your route is Great Lakes and Inland, those topics belong in your preparation. If your route is Inland only, applicability differs, and you should confirm against your approval rather than assuming. The same logic explains why the Rules module splits between Q100 and Q300.
| Item | Great Lakes and Inland route | Inland-only route |
|---|---|---|
| Rules module | Q100 (International and Inland), as approved | Q300 (Inland), as approved |
| Heavy-weather handling topic | Great Lakes-specific; study it | Confirm applicability with your approval |
| Launching lifeboats/liferafts in heavy weather | Great Lakes-specific; study it | Confirm applicability with your approval |
Why Your Approval to Test Controls Everything
The most important sentence in the whole process is this: your actual NMC approval to test controls your assigned modules, your applicable route, and any credit you receive. General outlines, including this one, describe the published module catalog. They cannot know whether you have credit for a module, whether your route changes the Rules choice, or whether Q352 applies to you.
That is also why this site avoids describing the credential as "one common mandatory examination." It is better understood as a set of route-aware preparation groups drawn from an official catalog, assigned individually.
- Read your approval line by line and list the modules it assigns.
- Match each assigned module to the group names above.
- Cross-check against the current NMC module-topic index rather than relying on older guides alone.
- Budget study time only for modules you are actually assigned.
For timing and logistics, see NM1GI Exam Dates: Testing Windows, Deadlines & Scheduling, and for money questions, NM1GI Certification Cost: Complete Pricing Breakdown.
Sequencing Your Preparation
Only a light touch of method belongs here, tied to the structure above. Because Rules and Chart Plot reward repetition, while Deck General and Deck Safety reward breadth, a sensible order front-loads the skills that need the most practice repetitions.
Rules of the Road (Q100 or Q300)
- Confirm which Rules module your approval assigns.
- Drill watchkeeping and the rule set for your route.
Chart Plot (Q350) and Navigation General (Q349)
- Practice plotting fixes, running fixes, and dead reckoning until method is automatic.
- Cover compass error, publications, and tides and currents.
Deck General (Q347) and Deck Safety (Q348)
- Work through the topic lists as checklists.
- Include the Great Lakes-specific heavy-weather items if your route requires them.
For a fuller plan, read NM1GI Study Guide 2026: How to Pass on Your First Attempt, and keep the one-page NM1GI Cheat Sheet handy for last-minute review. When you are ready to test yourself against realistic questions, the NM1GI practice test site is the place to start.
Frequently Asked Questions
On this site, NM1GI stands for National Master 100 GL and Inland: a U.S. Coast Guard credential for Master of vessels under 100 gross register tons on Great Lakes and Inland waters. The Coast Guard's exam listing for it is catalogued as GLI06.
The United States Coast Guard National Maritime Center governs it. Examination content, module assignments, and approval to test all come through that federal process rather than a private certifying organization.
Plan for five full-route preparation groups: Rules (Q100 or Q300), Deck General (Q347), Deck Safety (Q348), Navigation General (Q349), and Chart Plot (Q350). The route-specific Rules choice counts once. Your approval to test determines what you actually sit.
No. Q352, Navigation and Deck General/Safety, is a separately listed raise-of-grade route module. It is not a universal sixth group and not a second Rules subject. Study it only if your approval assigns it.
Not in the published materials this article draws on. Treat the five groups as unweighted preparation areas, and be cautious about any source quoting precise percentages. For related questions, see NM1GI Pass Rate: What the Data Shows and What Does NM1GI Stand For? for further background.