Assessing 155 Years of Hydrographic Survey Data for High Resolution Bathymetry Grids

Seafloor representation over vast areas requires the fusion of depth measurements from numerous data sets having variable spatial resolution and coverage. The most extensive coverage for U.S. coastal waters usually consists of data from hydrographic surveys conducted between 1850 and 2006. Intended for navigational charts, these survey projects have been planned, collected, and processed by the National Oceanic and Atmospheric Administration's National Ocean Service and its predecessor organizations over the past 155 years. Integrating the extremely dense and localized data from modern multibeam echo sounders with the much more significant area coverage of older survey data presents the fundamental challenge when creating high resolution coastal bathymetry grids. Data from nearly 7000 hydrographic surveys are being assessed to produce bathymetry grids for the coastal U.S. Every survey in the database is associated with metadata attributes summarized from the survey's descriptive report. Compiling high quality coastal bathymetry over extensive regions involves several hundred surveys whose range in age often spans over a century. Compared to survey measurements and the original hydrographic processing shortly after field collection, the greater uncertainties in representing the seafloor come from errors in the archive data retrieval processing that occurred years after field collection, as well as from the unknown depths between sparse soundings of historic surveys, whose interpolated values will constitute a substantial portion of gridded bathymetric coverage for the entire U.S. coast.