S-129 Under-Keel Clearance

S-129 is the IHO S-100-based product specification for under-keel-clearance management information, encoding computed UKC results, no-go areas, and dynamic depth advisories for a specific vessel and passage. Fed by S-102 bathymetry, S-104 water levels, and S-111 currents plus the ship’s draft and squat model, it lets an ECDIS or UKC service show real-time clearance margins along a route. IHO published S-129 edition 1.0.0 in 2019. It carries the result, not the raw hydrographic source data.