IHO S-101

IHO S-101 is the next-generation Electronic Navigational Chart product specification, built on the S-100 framework to replace the S-57 ENC. It carries richer feature and attribute coverage, improved portrayal driven by S-100 catalogues, and supports overlay with the other S-100 products such as S-102 bathymetry and S-104 water levels. The transition is staged: an ECDIS upgraded to read S-101 must keep reading frozen S-57 Edition 3.1 ENCs as well, and the IHO plans roughly a decade of dual-fuel operation before S-101 fully replaces S-57. S-100-capable ECDIS reaches navigational use from 2026, so officers will run mixed S-57 and S-101 folios for years.