New Edition Date
In the lower left corner of every chart, above the chart number, the edition number and the edition date are shown. However, NOAA Print-on-Demand (POD), Raster Navigational Chart (RNC), and PDF format charts (different formats of the same raster chart image) are updated and released to the public weekly.
Date of Last Chart Correction
Below the chart number, the date of the "Last Correction" applied to the chart is shown. Following that are the notice numbers and dates for the Local Notice to Mariners (LNM) and Notice to Mariners (NM) through which the chart has been "cleared."
Latest Date to which Chart is Up-to-Date
"Cleared through" information indicates the last notices that were checked for applicable changes. When a "Cleared through" date is later than the "Last Correction" date, this means that no LNM or NM changes were issued by the USCG or NGA for the chart after the "Last Correction" date. Thus, the chart is still up-to-date as of the cleared dates, even though no corrections have been applied in the intervening period.
Keeping Charts Up-to-Date
Paper chart users must check for and manually apply any applicable LNMs and NMs issued after the "Cleared through" dates. Users of digital chart formats may simply download another weekly update of the chart.
Inclusion of Non-Critical Data
Some of the updated raster charts that NOAA releases weekly may also include newly compiled information which does not originate from a notice to mariners. However, large changes, such as the addition of new hydrographic survey data, will usually result in a new edition of the chart being issued.