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 chart products, which include paper nautical charts and the corresponding digital raster navigational charts (NOAA RNC).
In the past, controlling depths – which are minimum depths measured during periodic USACE sonar surveys of channels – were indicated on raster charts. Going forward, controlling depths will no longer be shown and instead replaced with project depths, which are the original channel design dredging depths used by the USACE.
The USACE makes depth information from recent surveys publicly available on its website before NOAA nautical products are updated and published. NOAA’s priority is to update its suite of electronic navigational charts (NOAA ENC), so they are typically updated as much as one month ahead of their raster products. This means the raster charts often do not accurately reflect the most current controlling depths, or correspond with the controlling depths shown on the electronic charts and the USACE website. The decision to only show project depths on the raster chart products in future is intended to eliminate these inconsistencies.
Mariners are encouraged to use NOAA’s suite of electronic navigational charts for critical safety information as these products will not be affected by the change.