A nautical chart is never truly finished. The seabed shifts, wrecks appear, buoys move, and lights change, so the chart in your hands is only as safe as its most recent correction. If you have ever looked at a chart and wondered whether it still reflects reality, you are asking the right question.
Here is how often nautical charts are updated, how the correction cycle works for both paper and digital charts, and how to tell whether the chart you are navigating with is still current.
How Often Are Nautical Charts Updated?
Nautical charts are updated on two cycles at once. Small corrections are issued weekly through Notices to Mariners, while full new editions of a chart are published periodically, whenever accumulated changes or new survey data make a reprint necessary.
The weekly cycle handles individual changes: a relocated buoy, a newly discovered wreck, a changed depth, a discontinued light. Hydrographic offices such as NOAA and the UK Hydrographic Office publish these corrections every week so that mariners can keep charts current between editions. The edition cycle handles larger-scale change: when a chart has accumulated enough corrections, or when new surveys significantly revise the picture, the hydrographic office issues a completely new edition that supersedes the old one.
Understanding both cycles is the key to chart currency. A chart can be the latest edition and still be out of date if the weekly corrections since that edition have not been applied.
What Is a Notice to Mariners Correction?
A Notice to Mariners (NtM) is an official correction issued by a hydrographic office to update charts and publications with safety-critical changes. Each Notice carries only information that affects safe navigation, and mariners apply the relevant Notices to keep their charts corrected between editions.
For paper charts, corrections are traditionally applied by hand, with each Notice recorded on the chart and in a correction log. For digital charts, the updates are applied electronically. Either way, the principle is the same: a chart is only compliant and safe when it has been corrected to the latest available Notice. For the full explanation of how Notices work, how they are structured, and how corrections are applied, see the guide on understanding Notices to Mariners.
Paper Charts: Print-on-Demand and Currency
Not all paper charts are equally current, and this is where print-on-demand makes a real difference. A traditional paper chart printed months or years ago and held in inventory reflects the corrections that were current on its print date, and everything issued since must be applied by hand to bring it up to date.
A print-on-demand (POD) chart is different. Because it is printed at the time of order, a POD chart reflects the latest Notice to Mariners corrections available on that date. The buyer receives a chart already corrected to the moment of printing, rather than an older chart carrying a backlog of corrections to apply. For a recreational boater or a commercial vessel provisioning before a voyage, ordering a print-on-demand chart is the simplest way to start from a current baseline.
Even a freshly printed POD chart still requires ongoing correction for any Notices issued after the print date, so the correction discipline does not disappear. What POD removes is the backlog that a shelf-aged chart carries. The ANS nautical charts collection provides current paper charts for navigation and voyage planning.
Digital Charts (ENCs): Automatic and Manual Update Cycles
Electronic Navigational Charts (ENCs) are built for currency. Required for SOLAS Chapter V vessels, ENCs are delivered through services that push corrections on a regular cycle rather than requiring manual correction.
The ADMIRALTY Vector Chart Service (AVCS) delivers ENC updates weekly, by email, online download, or shipped media. New ENCs are added automatically to a vessel's folio holdings as they become available, so the chart outfit stays complete as coverage expands. AVCS also includes the ADMIRALTY Information Overlay, which displays Temporary and Preliminary Notices to Mariners directly over the ENC on the ECDIS, alerting the bridge to areas of navigational risk that a base chart alone would not show.
The update cycle is regular, but it is not automatic in the sense of requiring no action. The navigator must download and apply the weekly updates, and confirm that no charts or permits have lapsed. The process of ordering and updating ENCs is covered step by step in the guide on how to order and keep ENCs updated using SPICA. Current ENC services are available through the ANS digital charts collection.
How to Tell If Your Chart Is Out of Date
Checking whether a chart is current takes only a moment, and it is worth doing before every voyage. The practical checks are straightforward:
- Check the edition. Confirm the chart is the latest published edition. A superseded edition should be replaced, not corrected, because corrections restart against the new edition.
- Check the correction record. For paper charts, the last Notice to Mariners number recorded on the chart tells you how far it has been corrected. Compare it against the latest published Notice.
- Check the print date on POD charts. A print-on-demand chart is current to its print date; anything issued since must still be applied.
- Check ENC update status. On an ECDIS, confirm the last update was applied and that no permits have expired, which can cause charts to stop displaying.
- Watch for lapsed subscriptions. Digital chart permits and licenses expire, and an expired permit can remove a chart from the display entirely.
If a chart cannot be confirmed as current, treat it as suspect and verify it before relying on it for navigation.
Navigate on Charts You Can Trust
A nautical chart is a living document, corrected weekly and re-issued periodically to keep pace with a changing sea. Whether you navigate on paper or ENCs, currency is the difference between a chart you can trust and one that may already be wrong. Browse current nautical charts and digital chart services, or contact American Nautical Services at +1 (954) 522-3321 or sales@amnautical.com to provision a current chart outfit for your next voyage.
Frequently Asked Questions
How do I know if my nautical chart is out of date?
Check three things: whether it is the latest published edition, the last Notice to Mariners correction recorded on it compared to the current Notice, and, for print-on-demand charts, the print date. For ENCs, confirm the last update was applied and that no permits have expired. A superseded edition should be replaced rather than corrected.
How often are nautical charts corrected?
Hydrographic offices issue Notice to Mariners corrections weekly. These handle individual changes such as relocated buoys, new wrecks, and changed depths. Full new chart editions are issued periodically, whenever accumulated corrections or new survey data make a reprint necessary.
Are print-on-demand charts more current than pre-printed charts?
Yes. A print-on-demand chart is printed at the time of order and reflects the latest Notice to Mariners corrections available on that date. A pre-printed chart held in inventory reflects only the corrections current on its original print date, leaving a backlog to apply by hand.
How often should I update my ENCs?
ENCs should be updated on the service's weekly cycle. Services such as AVCS deliver updates weekly by email, online, or shipped media. The navigator must download and apply each update and confirm that no permits have lapsed, since an expired permit can cause charts to stop displaying.
What is the difference between a chart correction and a new edition?
A correction is a small update applied through a Notice to Mariners between editions, such as a moved buoy or a new wreck. A new edition is a completely republished chart that supersedes the previous one, issued when accumulated changes or new surveys make a reprint necessary. Corrections restart against each new edition.
