- What the Letters Actually Point To
- The Credential Behind the Acronym: GLI06 Master or Mate Under 100 GRT
- The Five Preparation Groups
- Why Your Route Changes the Exam
- Where Q352 Fits (and Where It Doesn't)
- Who Governs the Process
- Reading the Published Topic Catalog
- Sequencing Your Preparation Around the Groups
- Common Misreadings of the Acronym
- Frequently Asked Questions
- On this site, NM1GI means National Master 100 GL and Inland, the GLI06 Master or Mate less than 100 GRT route.
- The United States Coast Guard National Maritime Center governs the credential and your approval to test.
- Preparation is organized into five route-aware groups: Rules of the Road, Deck General, Deck Safety, Navigation General, and Chart Plot.
- The Rules group is Q100 or Q300 depending on your approved route, and it counts once.
What the Letters Actually Point To
If you have searched for "NM1GI" and landed on a confusing mix of results, you are not alone. The string is short, it looks like a code, and the internet is full of pages that use similar-looking acronyms for unrelated things. On this site, the meaning is narrow and specific: NM1GI stands for National Master 100 GL and Inland. It describes a mariner credential path, not a software product, not a medical specialty, and not a generic business certification.
Breaking the name into its parts helps:
- National signals a credential issued under United States authority rather than an international convention certificate.
- Master is the rank. The person holding it is qualified to command, not just stand watch under someone else.
- 100 refers to the tonnage ceiling. The scope covers vessels of less than 100 gross register tons (GRT).
- GL and Inland names the operating waters: the Great Lakes and inland waterways.
For a quick orientation to related phrasing, our short explainers on what NM1GI is and the meaning of the NM1GI label cover the same ground from slightly different angles. This article goes deeper into what the name implies for anyone preparing to test.
The Credential Behind the Acronym: GLI06 Master or Mate Under 100 GRT
In the Coast Guard's own examination listing, this route appears as GLI06, titled Master or Mate less than 100 GRT. The practical consequence of that title is worth pausing on. The listing covers Master or Mate in one route, but the identity we track here is the Master credential. When you read the NMC page for GLI06, keep that selected Master identity in mind rather than drifting into thinking only about the mate side of the shared route.
Because the vessels involved are under 100 GRT, the credential is relevant to a wide range of operations: small passenger vessels, towing and workboat activity, charter and excursion boats, and similar commercial work on the lakes and rivers. For more on how this plays out in employment, see our overview of NM1GI-related jobs.
The Five Preparation Groups
The most useful way to understand the credential is by the content you must master. The NMC publishes a catalog of modules and topics, and we organize it into five full-route preparation groups. These are unweighted. The NMC does not publish percentage weights for them here, so treat each group as something you must be ready for rather than a slice you can skip because it "counts for less."
Group 1: Rules of the Road (Q100 or Q300)
Either International and Inland (Q100) or Inland (Q300), according to your approved route. This group counts once, never twice.
- Watchkeeping
- COLREGS
- Inland Navigational Rules
Group 2: Deck General (Q347)
The seamanship and vessel-handling core, plus maritime law and shipboard management.
- Seamanship, marlinspike seamanship, and purchases, blocks, and tackle
- Vessel maneuvering: rivers and estuaries, shallow water, bank and passing-ship interaction, berthing and unberthing
- Anchoring and mooring, including dragging and clearing fouled anchors
- Heavy weather operations and maneuvering for launching lifeboats and liferafts in heavy weather
- Turn circle, pivot point, advance and transfer, and wake reduction
- Maritime law, credentialing of seamen, ship sanitation, hot work, ship's business, and required certificates and documents
Group 3: Deck Safety (Q348)
Stability, fire, and emergency response.
- Principles of vessel construction, trim, and stability; damage control
- Small engine operations and maintenance
- Fire prevention, firefighting appliances, fire drills, classes and chemistry of fire, and firefighting systems
- Emergencies: collision, temporary repairs, passenger and crew safety, fire or explosion, abandon ship, rescuing survivors, man overboard, and emergency towing
- Communications and signals: storm, wreck, distress, and special
Group 4: Navigation General: Great Lakes and Inland (Q349)
Position determination, compasses, weather, and publications.
- Piloting, distance off, bearing problems, fix or running fix, dead reckoning, and electronic navigation
- Aids to navigation; charts, navigation publications, and Notices to Mariners
- Magnetic and gyro compass principles, error, correction, and determination of compass error
- Meteorology and oceanography: weather systems, charts and reports, tides, and tidal currents
Group 5: Navigation Problems: Chart Plot (Q350)
The hands-on plotting group. You retain chart plotting as its own preparation area.
- Piloting, distance off, bearing problems, fix or running fix
- Chart navigation, dead reckoning, and electronic navigation
- Instruments and accessories, aids to navigation, and charts and publications
For a deeper walk through each of these, our complete guide to all five NM1GI content areas expands on the same structure.
Why Your Route Changes the Exam
A frequent point of confusion is the idea that there is "one" NM1GI exam that every candidate sits identically. The NMC material does not support that. These are route-aware preparation groups, not one common mandatory examination. Two things make this real:
- The Rules choice. Q100 covers International and Inland rules, while Q300 covers Inland only. Which one applies depends on your approved route. Because you take one or the other, the Rules group counts once toward your five.
- Great Lakes versus Inland applicability. The NMC table flags heavy-weather handling and the topic on launching lifeboats and liferafts with a footnote marking them as Great-Lakes-specific. If your approved route is Inland rather than Great Lakes, those topics may not apply to you in the same way.
| Variable | What changes | What to do |
|---|---|---|
| Rules of the Road | Q100 (International and Inland) or Q300 (Inland), by approved route | Confirm which module is assigned before studying |
| Heavy weather operations | Marked as Great-Lakes-specific in the NMC table | Check whether it applies to your route |
| Lifeboat and liferaft launching in heavy weather | Also marked Great-Lakes-specific | Check whether it applies to your route |
| Overall module list | Controlled by your approval to test | Treat the approval letter as the final authority |
Key Takeaway
Your individual approval to test is the controlling document. The published catalog tells you what the NMC can ask across the route; your approval tells you which modules, which route, and any credit actually apply to you.
Where Q352 Fits (and Where It Doesn't)
You may see Q352 Navigation and Deck General/Safety mentioned alongside this credential. It is a separately listed raise-of-grade route module. It is not a universal sixth group that every candidate adds to a full-original exam, and it should not be mistaken for a second Rules subject. If you are testing for the full original credential, plan around the five groups above. If you are pursuing a raise of grade, Q352 may enter the picture, and your approval to test will say so.
This distinction matters for planning time and cost. Candidates who assume a sixth module will inflate their study plan unnecessarily, while those who ignore Q352 on a raise-of-grade route will be caught short. To understand how eligibility and route interact, read our breakdown of NM1GI requirements, eligibility, and prerequisites.
Who Governs the Process
The governing body is the United States Coast Guard National Maritime Center (NMC). It publishes the examination listing for GLI06, the examination guide, and the module topic information. A few points on how to treat those sources:
- The NMC Examination Guide referenced here reflects regulations effective 2014-03-24. It should be used together with the current published NMC module-topic index and your individual approval to test.
- It is not a new 2026 universal exam specification, and you should not present it as one.
- Official percentage weights are not published in the material we rely on, so any site claiming precise percentage breakdowns for this route is going beyond the source.
Because pricing, scheduling, and eligibility details are tied to the NMC process and your individual approval, we point you to dedicated pages rather than guess here: NM1GI certification cost, NM1GI exam dates and scheduling, and what the passing score means.
Reading the Published Topic Catalog
The NMC topic catalog is more granular than most candidates expect. Rather than "navigation" as a vague bucket, it names specific skills such as determination of compass error, running fixes, and the effects of interaction with a bank or passing ship. That granularity is a gift: it tells you what a question can be built around.
Seamanship and vessel handling carry real detail
Deck General (Q347) is not just knots. It reaches into turn circle, pivot point, advance and transfer, which are the geometry of how a vessel actually turns. It covers wake reduction, vessel handling in rivers and estuaries, and the physical interaction between your hull and a nearby bank or passing ship. Expect to reason about cause and effect, not merely recall definitions.
Safety is procedural and sequence-driven
Deck Safety (Q348) leans on emergency procedure. Man overboard procedures, abandon ship procedures, emergency towing, and responses to collision, fire, or explosion are all listed. The value here is knowing the right order of actions and the reasons behind them.
Chart plotting is a skill, not a fact
Chart Plot (Q350) rewards practice with instruments and charts. You cannot memorize your way through a running fix. The listed topics (distance off, bearing problems, fix or running fix, dead reckoning) are all things you do with parallel rules, dividers, and a chart.
If you want a sense of how demanding this material is in practice, see how hard the NM1GI exam is, and for a condensed reference once you have the foundation, the NM1GI cheat sheet.
Sequencing Your Preparation Around the Groups
Generic study advice is plentiful, so here is only the part tied directly to this credential's structure. Because Navigation General and Chart Plot share piloting topics, and because Rules of the Road underpins how you reason about maneuvering and watchkeeping, a sensible order builds foundations first.
Rules of the Road
- Confirm whether your route assigns Q100 or Q300
- Work through watchkeeping and the applicable rules until situations feel automatic
Piloting and Navigation General
- Distance off, bearings, fixes, dead reckoning
- Compass error, aids to navigation, publications and Notices to Mariners
Chart Plot
- Drill plotting problems with real instruments
- Repeat running-fix and distance-off exercises until clean
Deck General and Deck Safety
- Maneuvering, anchoring, stability, fire, and emergency sequences
- Revisit route-specific items such as Great-Lakes-only heavy-weather topics
This is a template, not a mandate. Adjust it to your experience: a working tug deckhand may need less seamanship time and more plotting practice, while someone from a non-deck background may need the reverse. Our full NM1GI study guide develops longer-form planning, and the practice test site lets you check where you actually stand before committing to a schedule.
Common Misreadings of the Acronym
Because the label is compact, it gets misread. Here are the most common errors we see, and what the credential actually involves.
| Misreading | Reality for National Master 100 GL and Inland |
|---|---|
| "It is one fixed exam everyone takes identically." | These are route-aware preparation groups; your approval to test controls the assigned modules. |
| "There are six exam groups." | There are five full-route groups; Q352 is a separate raise-of-grade module. |
| "Rules of the Road counts as two subjects." | It counts once: Q100 or Q300 by approved route. |
| "Every topic applies to every candidate." | Heavy-weather and lifeboat/liferaft launching topics are marked Great-Lakes-specific. |
| "There are published percentage weights." | Official weights are not published in the source material used here. |
| "The guide is a new 2026 specification." | The examination guide reflects regulations effective 2014-03-24 and must be used with current NMC indexes. |
Another recurring question is whether the label refers to something broader, such as a general safety or business credential. It does not. If you want the alternate phrasing explained, our pages on what NM1GI stands for and the NM1GI certification itself address the same identity from other directions. If you are weighing whether the effort makes sense for your career, the ROI analysis and earnings guide are the next stops, and for the numbers behind outcomes, see what the data shows on pass rates.
Key Takeaway
When someone asks what NM1GI means, the accurate answer is a chain: National Master 100 GL and Inland, GLI06 Master or Mate less than 100 GRT, governed by the Coast Guard National Maritime Center, prepared for through five route-aware groups.
Frequently Asked Questions
It means National Master 100 GL and Inland, the GLI06 Master or Mate less than 100 GRT route issued under the United States Coast Guard National Maritime Center. It refers to a command-level mariner credential for vessels under 100 gross register tons on the Great Lakes and inland waters.
The United States Coast Guard National Maritime Center governs it. It publishes the GLI06 examination listing, the examination guide, and the module topic information, and it issues the individual approval to test that controls your assigned modules.
Plan around five route-aware groups: Rules of the Road (Q100 or Q300), Deck General (Q347), Deck Safety (Q348), Navigation General: Great Lakes and Inland (Q349), and Navigation Problems: Chart Plot (Q350). Q352 is a separate raise-of-grade module and is not a sixth group for a full original.
No. It counts once. Depending on your approved route, you will be assigned either Q100 (International and Inland) or Q300 (Inland), not both as separate groups.
Official percentage weights are not published in the material this article relies on. Treat the five groups as unweighted preparation areas, and use your approval to test as the final word on what you will actually be examined on.
The acronym is short, but the credential behind it is specific and well documented by the Coast Guard. Start from the identity, confirm your route and approved modules, then build your preparation around the five groups. When you are ready to test your knowledge against realistic questions, the NM1GI practice test site is a good place to begin.