IHO S-102

IHO S-102 is the Bathymetric Surface product specification in the S-100 family, carrying gridded depth as a continuous surface rather than the spot soundings and contours of an ENC. Each grid node holds a depth value and an uncertainty, so an S-100-capable ECDIS can shade the seabed at high resolution and compute under-keel clearance against the actual bottom shape. Overlaid on an S-101 ENC and combined with S-104 water-level data, S-102 lets a ship plan a tidal window across a shallow channel far more precisely than fixed safety contours allow. It is a key enabler of dynamic under-keel clearance management in ports.