NOAA Announces Change in Channel Depths on Raster Charts

NOAA’s Office of Coast Survey recently announced plans to change the U.S. Army Corps of Engineers (USACE) maintained channel depth values on raster nautical chart products, which include paper nautical charts and the corresponding digital raster navigational charts (NOAA RNC®). Minimum depths (also called controlling depths) are collected during periodic USACE sonar surveys of channels. In the past, these depths were provided on raster charts, but controlling depths will now be replaced with the original channel design dredging depths used by the USACE (called project depths). Standardizing depth presentation on these products will improve data consistency and overall safety. Implementation begins in early 2019.

NOAA’s suite of electronic navigational charts (NOAA ENC®) are not affected by these changes. Mariners are encouraged to use NOAA ENCs for critical safety information as these products are typically updated up to one month ahead of raster products.

Why the change?

The USACE makes the depth information from recent surveys publicly available on their website before NOAA nautical products are updated and published. NOAA prioritizes making updates to ENC over RNC products. This often results in RNC products not accurately reflecting the most current controlling depth values (as represented on NOAA ENC and the USACE website). To eliminate inconsistencies among controlling depths, NOAA will only show project depths on raster chart products in the future. The Initial implementation of this change will focus on deep draft shipping channels where the primary product used for navigation is the ENC. 

How will mariners be notified?

NOAA first publicized the concept of charting project depths in the National Charting Plan released in February 2017. As the changes are made on individual charts, NOAA will include a note on each chart directing mariners to review the USACE website and use NOAA ENC to access the latest controlling depths. Additionally, a statement drafted jointly by Coast Survey and the U.S. Coast Guard is being published weekly in the Coast Guard’s Local Notice to Mariners.

For detailed information on these changes, please visit https://www.nauticalcharts.noaa.gov/updates/?p=171708.