Ships must practice celestial navigation

The amphibious assault ship USS Essex in the Gulf of Aden.
Navy photo by Mass Communication Specialist 3rd Class Matthew Freeman

From USNOI by Walter O’Donnell and Caroline Stanton Chlaupek

 

In February 2022, the USS Essex sailed from Hawaii to California using only celestial navigation methods.
This is what the navigation team learned and why all ships should make similar voyages.

In February 2022, just a few miles off the coast of Oahu, Hawaii, all electronic navigation systems on the bridge of the USS Essex (LHD-2) went dark.
The bridge team shifted to navigating by celestial fixes plotted on paper charts.
Five days and more than 1,800 nautical miles later, the Essex arrived off the coast of San Diego, California, on time and on track.

A casualty did not cause this to happen.
With the approval of the Essex’s commanding officer (CO), Captain Kelly Fletcher, her navigator (coauthor and then–Lieutenant Commander Stanton), and the lead navigation instructor from Surface Warfare Schools Command in Newport, Rhode Island (coauthor Walter O’Donnell), the Essex tested its own proof-of-concept for navigating with a total loss of integrated electronic navigation equipment.
Any navigation equipment that used electricity was prohibited, including all GPS sources, the Essex’s electronic Voyage Management System (VMS), and the computer-based celestial navigation software STELLA.

Celestial navigation competence was still necessary just a generation ago.
The practice waned with the advent of more sophisticated and precise electronic navigation solutions; yet, as U.S. adversaries’ cyber and electronic warfare capabilities advanced, analog navigation techniques became relevant again.
However, it is still rare for a Navy warship to intentionally operate without its electronic navigation suite.
As The American Practical Navigator (aka “Bowditch”) states, “No navigator should ever become completely dependent on electronic methods.
The navigator who regularly navigates by blindly pushing buttons and reading the coordinates from ‘black boxes’ will not be prepared to use basic principles to improvise solutions in an emergency.”1

The coauthor, right, and one of her quartermasters on board the USS Essex (LHD-2) plot a course in the ship’s pilothouse.
To ensure the bridge watchstanders could keep a precise and continuous paper plot, Lieutenant Commander Stanton required practice plots during both deployment transoceanic transits (San Diego to Guam, then Japan to Oahu).
U.S. Navy (Walter O’Donnell) 

The Five-Day Exercise

The Navy conducts live-fire weapons drills, damage control drills with real smoke and fire, and exercises hunting real submarines, but it does not regularly practice for emergency, long-term, open-ocean navigation without GPS.
With many vulnerabilities, GPS will likely be the first system an adversary attempts to disrupt during a war. 2 

Captain Fletcher approved this electronics-denied voyage to assess her crew’s navigation capabilities under pressure.

Navy navigators are held to an exacting standard in shiphandling, piloting, seamanship, planning, and ocean sailing.
In addition, navigators juggle many administrative tasks, such as department head and senior watch officer duties and preparations for material and administrative inspections. 3

At the same time, The Surface Ship Navigation Department Organization and Regulations Manual(NavDORM) expects that “ships will be prepared to operate in a PNT [position, navigation, and timing] degraded or denied environment.” 4

But a navigator must be always ready and able to do so.

In 2017, naval training curricula reinstated basic celestial navigation topics, ensuring junior surface warfare officers and quartermasters are oriented to fundamental concepts and vocabulary prior to entering the fleet. 5 

However, mastery of such a complex skill requires dedicated practice at sea.
The Essex’s five-day celestial navigation transit should be a training template for future navigators, junior officers, and quartermasters.

Preparation and Methodology

Prior to deployment, Lieutenant Commander Stanton conducted a celestial navigation training series for junior officers and quartermasters of the watch (QMOWs).
The series moved from theory to practice, culminating in a hands-on sextant exercise from the Essex’s flying bridge.
To ensure the bridge watchstanders could keep a precise and continuous paper plot, Lieutenant Commander Stanton required practice plots during both deployment transoceanic crossings (San Diego to Guam, then Japan to Oahu).
The celestial plots, including a continuous plot of dead reckoning positions, were compared directly to GPS, VMS, and STELLA to hone celestial navigation skills while all sensors were still available.
For maximum training effect and redundancy, two paper celestial plots were always maintained on the bridge: one by the officer of the deck and the junior officer of the deck, and another by the QMOW.

Captain Fletcher reviewed and approved a detailed safety plan that minimized risk at all stages of the exercise.
Lieutenant Commander Stanton planned the voyage on a paper gnomonic chart and in VMS, then the chart petty officer laid the track on position plotting sheets for both the junior officer plot and the QMOW plot.
Lieutenant Commander Stanton reviewed available celestial bodies for the planned latitudes as well as the weather forecast for predicted sky cover percentage.
During the voyage, the only operational VMS nodes (with GPS) would be in the combat information center (CIC) and the chart room.
All other nodes (QMOW table, officer of the deck station, navigator’s stateroom, and VMS repeater in the CO’s cabin) were configured to keep them online for system health, but with the display unavailable to all users.
The chart room node was used exclusively for the QMOW to log the ship’s position per NavDORM requirements.
However, Lieutenant Commander Stanton’s guidance was to look only at the coordinates on the display and keep the view offset.
CIC was to notify Lieutenant Commander Stanton if the Essex deviated more than 10 nautical miles (nm) from the planned track.

A quartermaster on board the Essex plots a course in the pilothouse.
The Essex’s celestial navigation voyage gave the watch officers and quartermasters the opportunity to toil over a paper plot, watching their hand-drawn symbols move from west to east.
U.S. Navy (Brett McMinoway)

The Transit—a Firsthand Account and Impressions

During the five-day, 1,800-nm transit, the navigation team and bridge watchstanders did not use GPS, STELLA, VMS, or any GPS-derived information, including course/speed over ground.
When we obtained two consecutive fixes, we calculated set and drift and course/speed made good.
We used pilot charts (historical weather charts) to help predict expected leeway, set, and drift over the course of the voyage.

We had a steep learning curve on the first day without electronics.
The ship ended up 5 nm off track.
In the Pacific Ocean, a 5-nm track deviation is not navigationally significant; however, it was significant to us because we expected (perhaps unrealistically) immediate precision.
Fortunately, Captain Fletcher continued to trust the team.
For the rest of the voyage, the ship remained within 2 nm of track, and on reaching San Diego, we were consistently plotting within 1 nm of track.

While we expected precision, we had to learn to wait longer and use fewer fixes to achieve it.
We routinely navigated for 12 hours at night without a fix, when celestial navigation is all but impossible without advanced, expensive equipment (i.e., a bubble sextant).
Twice during the voyage, more than 15 hours elapsed between fixes because of cloud cover.
While this length of time may not surprise those who sailed prior to GPS, it is gut-wrenching in today’s Navy after years of easy access to precise, real-time data and communications.
Should maintaining a celestial navigation plot become necessary in the future, bridge watch officers and all who rely on their position data will be required to do what has become unnatural at sea—wait.
Lessons

Advanced, hand-computed celestial navigation is a full-time job.
It required both of us to be on (or near) the bridge for approximately 18 hours a day, especially during the morning and evening star fixes.
Performing sight reduction by hand required approximately three to four hours per day.
Navigators who aspire to conduct a similar voyage may use STELLA to avoid cumbersome hand computations.

The surface warfare junior officers and quartermasters loved this evolution.
No longer able to stare at the VMS screen, they were liberated from the temptation to make micro course adjustments to keep the ship perfectly on the electronic track line.
Not only did this save fuel, but it also gave the watch officers and quartermasters the freedom to enjoy being what they called “real sailors” as they toiled over a paper plot.

Patience and foresight are required.
When a ship configured with GPS and VMS makes a course or speed change, there is immediate feedback.
However, with these systems no longer in play, navigation teams must rely on past solutions to predict future success.
For example, after plotting an evening star fix and obtaining the ship’s position, we calculated set and drift, noted how far left or right of track the ship was, then chose a course to correct our position in relation to track while compensating for observed set and drift.
We were unable to obtain feedback on our decision until after our morning star fix—typically 12 hours later.
Since the length of time between observations is so long, solutions must be minor and meticulously considered.
For example, using the radian rule, steering 1 degree off base course for 12 hours at a speed of 16 knots results in nearly 3.5 nm left or right of track (565 yards per hour).

Most navigators and senior QMs have the training to complete a similar voyage.
Any Surface Navigator/Assistant Navigator Course or QM A School graduate can perform celestial navigation using only STELLA, paper charts, and plotting sheets.
However, while being trained in the competencies of the craft, many navigators and quartermasters do not practice celestial navigation regularly in the fleet.
Despite the fact that since 2015 the NavDORM requires that each ship conduct a celestial navigation Day’s Work in Navigation (DWIN) daily, Mr. O’Donnell has asked more than 1,000 Surface Navigator/Assistant Navigator students if they had done one and fewer than half said they had, with most admitting that celestial navigation is the first part of their jobs they sacrifice to fulfill their administrative duties.
Despite the Chief of Naval Operations’ emphasis on celestial navigation, a culture of using celestial navigation daily has yet to be embraced again in the surface fleet.

Recommendations

Whenever possible, navigators and quartermasters should take the celestial navigation skills they learned in the classroom, practice them at sea, and lead by example.
Use the sextant at least once a day.
Master sunlines first, then planets, stars, and finally the moon.
Earn the commanding officer’s and executive officer’s trust before asking them to embark on a celestial navigation voyage.

Start small and get creative.
Unplug the Defense Advanced GPS Receiver (DAGR) on the emergency navigation laptop.
Manually update the ship’s ENL position using celestial fixes for a few days, with the goal of doing it for a full voyage.
Once acceptable accuracy has been achieved, go the next step and plot on charts and paper plotting sheets.
Varsity-level celestial navigation is a full paper plot with sight reduction done by hand.
This is the most primitive way of navigating, and mastery of it will ensure ships’ navigation teams can endure wartime conditions.

Commanding officers must trust their navigation teams.
COs will set their ship’s safety boundaries during any celestial navigation practice, and navigation teams should be free to grow as they learn within those boundaries.
COs should ensure their navigation teams are completing the DWIN checklist (Appendix K in the NavDORM) every day, as the type commanders require.6 To hold navigation teams accountable, have the navigator submit the previous day’s DWIN checklist with 12 o’clock reports while underway.
COs should take their navigators off the watchbill whenever possible so they can focus on completing and teaching celestial navigation.

Finally, ships should conduct an analog voyage on every extended transit, specifically crossing the Atlantic or Pacific Oceans.
Navigators should be given autonomy and authority to tailor their methods as their teams grow more competent.

If any ship is interested in undertaking a similar voyage, we can send them a training plan and offer distance support as they prepare.
The USS Porter (DDG-78) completed a similar crossing of the Atlantic Ocean in June 2023 after her navigator and senior QM expressed interest.

In the GPS-addicted Navy, an analog voyage over long distances is a novel concept.
But we did it, and other ships can, too.
In wartime operations, they may have no choice.

Links : 

• 1. National Geospatial-Intelligence Agency, The American Practical Navigator (Springfield, VA: National Geospatial-Intelligence Agency, February 2024).
• 2. LCDR Nicholas Monacelli, USCG, “Regaining the GPS Strategic Advantage,” U.S. Naval Institute Proceedings 147, no. 4 (April 2021); LT Mark K. Jbeily, USN, “Satellites in the Crosshairs,” U.S. Naval Institute Proceedings 147, no.
  6 (June 2021); Dana Goward, “Patterns of GPS Spoofing at Chinese Ports,” The Maritime Executive (December 2019); and ADM Michael Gilday, USN, Chief of Naval Operations Navigation Plan (January 2021).
• 3. Department of the Navy, Naval Surface Force/U.S. Pacific Fleet, ComNavSurfPacInst 3530.4G: Surface Ship Navigation Department Organization and Regulations Manual (28 October 2021).
• 4. Surface Ship Navigation Department Organization and Regulations Manual.
• 5. Gareth Evans, “Celestial Navigation: Ancient Craft Reinstated as Cyber Warfare Looms Large,” Naval Technology, February 2016.
• 6. Surface Ship Navigation Department Organization and Regulations Manual, Appendix K.
• GeoGarage blog : Celestial navigation / US navy returns to celestial navigation amid fears ... /
  How ancient navigation techniques can still help sailors ... / The U.S. Navy's new unhackable GPS alternative: the stars / 8 tools we used to navigate the world around us before ... 
• AppStore : Celestial Navigation

China’s control of submarine cables between NATO nations under scrutiny

CITIC Telecom's Baltic Sea Cable
Fiberoptic cable connecting Estonia, Finland and Sweden

From Newsweek by Brendan Cole and John Feng

A Finnish newspaper has reported growing security concerns in the country over the Chinese ownership of a firm that operates underwater data cables in the Baltic Sea.

Helsingin Sanomat reported that there was increased scrutiny over the Chinese state-owned firm Citic Telecom CPC, through its subsidiaries, owning the three telecommunications cables linking Finland, Estonia, and Sweden.

 

Although there are no allegations of wrongdoing by the firm, the head of Finland’s National Cyber Security Centre told the paper that Beijing's link was of concern because whoever controlled the cable had access to its data traffic.

Sari Arho Havrén, senior adviser for Business Finland, told Newsweek that as the cables are critical infrastructure, their control by China “is indeed problematic.” 

Why It Matters

 
Finland, the European Union, and the United States have recently raised concerns about Beijing’s links to data cables, citing worries about national security, data integrity, and geopolitical stability over this vital infrastructure for NATO countries.

What To Know

The story by Helsingin Sanomat outlines how Citic Telecom CPC company, through its subsidiaries, owns and operates three Baltic Sea cables that carry information from private individuals, companies, and authorities.

A map by Newsweek illustrates the extent of this network, which comprises three separate routes: one between Finland and Estonia, a second between Finland and Sweden, and a third between Estonia and Sweden. 

Citic Telecom CPC is headquartered in Hong Kong, but its parent company, Citic Group, is owned by the Chinese state and operates under the supervision of China's Ministry of Finance, playing a key role in China’s Digital Silk Road initiative.
This initiative is expanding Chinese tech infrastructure globally.

The three cables in the Baltic Sea are managed by Citic Telecom CPC's subsidiary in Tallinn, according to Helsingin Sanomat, which quoted the company as saying that it operates under EU regulation and fully complies with local laws and regulations.

There was little attention when it acquired the data cables from the Dutch company Linx in 2019, but growing concerns have since emerged over Beijing’s more assertive foreign policy and increased role in the internet cable network. 

In Estonia, Citic’s subsidiary provides services to the Defence Forces, Ministry of Education and Research, and Narva City Administration, the paper said.

Traficom, the Finnish communications agency, has not detected any misuse related to Citic Telecom CPC's data cables in the Baltic Sea.

However, Anssi Kärkkäinen, Director General of the National Cyber Security Centre Finland (NCSC-FI) told the outlet that ownership of data cables always involves a risk and as critical infrastructure, whoever controls them has access to their data traffic.

In recent months, the authorities of Finland, the European Union and the United States have raised concerns about data cables owned by Chinese companies.

In 2022, the U.S. banned one of the Citic Group's telecommunications companies from operating in the country, and the European Parliament raised the issue of trade in its resolution on China's cyber threat.

Sari Arho Havrén, who is also an associate fellow at the Royal United Services Institute (RUSI) told Newsweek Thursday that following accusations of cables being cut and China’s backing for Russia and its war against Ukraine “these hidden risks are attracting more attention."

China's increasing influence over the internet cable network and the potential threats to modern societies and their reliance on these networks are becoming more evident and critical infrastructure; its control by Beijing was problematic, she said. 

The C-Lion1 submarine telecommunications cable being laid at the bottom of the Baltic Sea off the shore of Helsinki, Finland, on October 12, 2015.
(Ph...Read More

What People Are Saying

Anssi Kärkkäinen, Director General of the National Cyber Security Centre Finland (NCSC-FI), told Helsingin Sanomat: "From our point of view, all submarine cables are critical infrastructure...whoever controls the cable has access to the data traffic on it, if they so wish."

RUSI Associate Fellow Sari Arho Havrén told Newsweek: “These cables are critical infrastructure, and their control by China is indeed problematic.” 

What Happens Next

The Chinese firm is not accused of wrongdoing, but scrutiny is likely to remain over China's Digital Silk Road Initiative.
Reuters reported in July that the U.S. plans for new regulations that would more extensively ban the use of Chinese technology in data cables and limit the granting of new licenses to Chinese cable companies.

Whales cemetery in Yanrakynnot Chukotka (Russia) honors the spirits of whales

Un cimetière géant au bout du monde.

Tchoukotka, Extrême-Orient russe pic.twitter.com/lMSQcAcxJi

— Renard Jean-Michel (@Renardpaty) October 8, 2025

Links :

• PetaPixel : Photograper Explores Whale Cemetery and Crashed Soviet DC-3 Between Worlds

 

U.S. military destroys 20th suspected drug boat

The US strikes four suspected drug boats in the eastern Pacific Ocean.

Defense Secretary Pete Hegseth released video of the strikes on X.

He says there were three strikes on the boats Monday, killing a total of 14 "narco-terrorists."

Mexico took over the search for one survivor.

President Donald Trump has been targeting drug-trafficking boats heading for the US off the coasts of Latin America since September.

 

From Maritime Executive

 

 The U.S. military has killed another four suspects in its new airstrike campaign against suspected smuggling boats off Latin America, according to CBS and the New York Times.

The strike is the 20th in the series, and brings the total number of deceased to 80 people.

Pentagon officials confirmed the attack to both outlets, but a formal announcement of the action is still pending, reportedly because top officials are awaiting video footage.

The attacks are controversial in legal circles, both for its compliance with American law and for compliance with international human rights law, and have attracted scrutiny. 

"The US must halt such attacks and take all measures necessary to prevent the extrajudicial killing of people aboard these boats, whatever the criminal conduct alleged against them," said UN High Commissioner on Human Rights Volker Turk last week.

Colombia has ceased sharing intelligence with U.S. forces over its concerns about the strikes, and the United Kingdom has decided to stop reporting the movements of suspicious boats in the Caribbean to the U.S.-led counternarcotics consortium, Joint Interagency Task Force West. 

The family of one of the deceased, Colombian fisherman Alejandro Carranza, has promised to sue the administration in U.S. courts for wrongful death; they have already retained an American attorney.

Out of 20 strikes, only two survivors have been rescued, one Colombian and one Ecuadorian national. Both have been repatriated, and the Ecuadorian national has been released without charges because of lack of evidence.

The Pentagon has pledged that the attacks will continue.

In addition, it is building up a substantial task force near Venezuela's coast, consistent with a large-scale military action.

Sources within the department have told CBS that while no decision has been made to move ahead, the president has been briefed on possible strike options, to include attacks on land targets.

The carrier USS Gerald R. Ford is now approaching the staging area, bringing four squadrons of F/A-18 Super Hornet strike fighters and three additional destroyers - enough capacity to consider a sustained air campaign.

 

NOAA's new nautical chart numbering system

ENC US coverage on Google Earth with GeoGarage weekly updated kmz

From David Burch blog

Official US charts with chart numbers started with the founding of the US Coast Survey in 1807 that evolved through several forms into the modern NOAA.
Historic charts can be tracked down at historicalcharts.noaa.gov.

The first Boston Harbor chart, for example, was called No. 337 in 1836.

Boston Harbour N°337 / courtesy of old-maps.com

see 1864 version in high resolution with Oceangrafix 

 

It was then replaced with No. 246 in early 1900s, and then in 1974 the system many of us grew up with was established.

 

And then this chart was called 13270, a number that lasted until its final edition, when all paper charts were discontinued at the end of 2024.

That numbering system grouped charts using the first two digits as follows:

19xxx = Hawaii charts
18xxx = Pacific Coast and Salish Sea Charts
17xxx = SE Alaska
16xxx = Alaska 14xxx = Great Lakes
13xxx = Atlantic, Long Island to Maine
12xxx = Atlantic, Cape Hatteras to N end of Long Island
11xxx = Gulf Coast and Atlantic up to Cape Hatteras

To reminisce on this and learn all those chart numbers, see How to Get a Copy of a Discontinued NOAA Chart.

With the demise of the NOAA paper charts—which brought with it the end of all raster navigational charts (RNC)—the only official charts left were the electronic navigational charts (ENC).
The "sunsetting" of the paper charts should not have been a surprise; it was announced in 2019 and they began the process almost immediately.

Many mariners first confronted ENC this year, but they are not at all new.
They were defined by the IMO and IHO in 1990, approved for use in 2000, and they have been mandated to be used by all SOLAS vessels since 2018.

NOAA's first official ENC were published in 2003.
The original NOAA ENC (now called legacy), some of which are still in use, especially on the West Coast, have wildly irregular shapes, and multiple scales (over 100!), that come about from the strict IHO rules on how they must match up and not overlap, yet stemming from existing paper chart data.
Below is a sample from the Eastern Strait of Juan de Fuca.

Here we see legacy ENC along with the RNC (paper charts) they were based upon, plus the prominent lack of chart around Victoria BC, due to the IHO rule that no two nations can make an ENC of the same area.

The shapes and scales of the legacy ENC are chaotic, but the file names (chart numbers) are in fact fairly systematic.

The chart number starts with the originator's country code (US) followed by the scale band of the chart, which is the compilation chart-scale range for legacy ENC, followed by the state abbreviation (USPS conventions), followed by two digits which is the chart ID, and that is followed by an "M."

No one seems to know why this is an M.
We do know the full name according to IHO must be 8 characters, so they needed something.
Some have suggested it means metric, but we do not need to be told that because all ENC, worldwide, must be metric, plus others have said there is no evidence this means metric.
The "no one," "some," and "others" refer to NOAA personnel, over the years.

So, for example, chart number US5WA16M means:
US = United States made the chart
5 = scale band 5, which in legacy terms means 1:5,000 to 1:51,639
WA = Washington state chart
16 = chart ID
M = filler to make 8 characters

Note that ENC retain chart names (as opposed to chart numbers), similar to the paper chart names they were based upon.
US5WA16M, for example, has the name "Approaches to Admiralty Inlet, Dungeness to Oak Bay."

Here are the scales in use

There is a detailed explanation of the rescheming program on line at Rescheming and Improving Electronic Navigational Charts.

The rescheming began slowly in late 2019, early 2020, which introduced a new numbering system, but it was not described on a NOAA website till mid 2024.
I have since discovered that it was indeed presented on an IHO website in 2017 and then updated at the IHO in 2020.

The new chart numbering system was not noticed much because the rescheming was slow getting started, and we had most of the time just a few reschemed charts amid mostly legacy versions—as we have now in WA state.
But the rescheming is now nearly done elsewhere, and the new numbering has since been added to the latest rescheming overview.
Recent rescheming progress has been very good.

There are still 8 characters to the name of every ENC worldwide, and they still start with the national IHO Producers Code (US, CA, FR, GB...), followed by the scale band, but the meaning of the rest of the characters is new.

The regional code replaces the simple US state abbreviation, and the cell location within a matrix replaces the previous (chart number + M).

In principle, and in some cases, this is a simple system.

For example look at scale band 3 charts in Louisiana (LA).

The above are scale band 3 charts for LA with neighboring charts from TX, MS, AL, and FL.
Green ones are available now.
Red ones are planned.

Many states, such as LA, have only one regional code, which is the state abbreviation + 1, LA1 in this case.
So all charts in the state use regional code LA1.
Other states like CA, WA, NY have multiple regional codes, i.e., WA1, WA2, WA3, etc.

We see that the SW corner is cell location (A, A); they then increase to the north and east, ending when it reaches a neighboring regional code.

It would be nice to stop at this point saying that is the new system, but that would leave out some details that might confuse us when encountered.

First, we note that for scale band 5, the regional code based on state ID can be replaced in the vicinity of some specific ports with its United Nations Location Code (UN/LOCODE).
Also when multiple state codes are used, it is not always clear what the logic is for their specifications.
See for example, this plot of scale band 5 charts of NY.

These are scale band 5 for NY state, with some NJ, RI, and CT.
The sizes are all the same, but the scales vary—in principle either 1:12,000 or 1: 22,000, but some of these have not been updated so they are still 1:10,000 and 1:20,000.

But looking at how they are named, we see the influence of the new rules.

NY has more than 1 region code, and on scale band 5 they use NY1, NY2, and NY9.
In California, scale band 5 uses CA1, CA2, CA3, and CA4, which appears to be latitude and scale band dependent.
In NY, the codes seem to be longitude dependent, but not in sequence.

Also in NY we see the use of three UN/LOCODES: NYC (New York City), HEP (Hempstead), and PTJ (Port Jefferson).
The location code abbreviations are likely understood by local mariners, but likely less so by visitors.
Zoom in on the charts, and it should be clear what they refer to.

Just about every city in the world has a UN code, which mariners might be familiar with on some level, because the ones that are ports are used in Type-A AIS voyage data for the reported destination.
That AIS output is manually entered, and mariners can put what they want, but the intention is to use the UN codes, which is common.
Looking at the practical side, however, many ships forget to change this once they leave a port.
So often the destination broadcasted is actually where they just left from!

So the summary is, most ENC chart names still include the state, but it will be followed by a number whose whose meaning may not be obvious and may depend scale band.

The exceptions are the scale band 5 charts that instead of the state regional codes, will (on just a few charts) use UN codes for what NOAA refers to as "Principal ports (based on cargo, fisheries, and tourism)."

NY uses three of these, one of which is certainly more "principle" than the other two.
CA charts in production propose to use four of these: OAK (Oakland); NTD (Port Hueneme); LGB (Long Beach); and SAN (San Diego).
One might not have guessed that Port Hueneme (why-NEE-mee) made the list, but we probably learn more about this port because of this.

The UN/LOCODES are also used in principle for scale band 6 ENC, but NOAA does not yet have any of these—and the couple we used to have are now discontinued.

The last point to address is the cell location ID at the end of the file name.
It is based on a matrix, unique to the state and to the scale band, whose SW most cell is called AA.
In some cases, as above for LA scale band 3, the pattern is clear.
In other chart regions it is not clear, and what we see in the SW corner is a matrix location that is not easy to decipher.

Below is a sample of where the DE and NJ charts meet.

 

 
The NJ charts look fine with AA in the SW corner, but the DE charts start with DE in the SW corner—which is just a coincidence that is trying to fool us!

It has nothing to do with the state abbreviation.
This is the D row of the E column, with the location of the non existent AE chart indicated here in red.
This chart has not been created yet, but it might be once the legacy chart US5DE10M gets reschemed. 

And to see why this is AE instead of AA, we have to look to the NW.
Delaware has charts running up the Delaware Bay, as shown below.

 

Again, the sequence of DE charts (blue) runs into a legacy chart (USDE13M) that has not been reschemed.
Once that is done, we see where there might be a chart LA next to the existing LB, which would mark the A column that we can extend south to see the matrix location of a chart AA—if it were to exist.
A key to understanding this cell location system is to realize that there does not have to be an actual chart for every location in the grid.
Notice that FF is missing in the southern DE graphic.

 

So it seems that NOAA starts by defining an area that is going to be reschemed at, say, scale band 5.
Then they lay a rectangular grid of scale band 5 charts over that area, which are labeled starting with AA at the SW corner.
Then wherever they produce a chart within that grid, it gets the grid label for that specific location.
In some cases the AA location will be a real chart, but in many others it will not.

Hopefully this helps understand the intended matrix system.

So we have a new chart naming system that is better than the paper chart "eighteen-thousand means West Coast," and better than the legacy ENC system, which added a state designator, but the rest the name conveyed no information, and could be very misleading.

In US5DE13M, shown above, for example, the same chart covers three different locations, separated by as much as 20 nmi, and adjacent legacy chart numbers had no relationship to each other.
We knew that system had to go, and now it is nearly done. 




Links :

• Burch YouTube : History of US Nautical Chart Numbers
• GeoGarage blog : Rescheming and improving Electronic Navigational Chart / Rescheming and improving Electronic Navigational Charts / Rescheming and improving GB Electronic Navigational ...