ABSTRACT Bathymetric and bottom data are a primary tool of marine commerce, industry, and research. Traditionally, these data have been shown on nautical and bathymetric charts produced by the National Oceanic and Atmospheric Administration's (NOAA) National Ocean Survey (NOS). Because nautical charts are specifically designed for navigators, they often do not meet the needs of the non navigation-oriented users of bathymetric and bottom data. The restrictions of nautical chart usage have been overcome largely through digitization of a large volume of marine charting data. These digital data, consisting of more than 40 million soundings, bottom characteristics, dangers to navigation, and shoreline points, have been acquired by NOAA's Environmental Data Service for distribution to the public. Both versatility and accessibility of coastal data have improved significantly because of computerization. Large volumes of soundings can be quickly and efficiently assimilated or synthesized by computer, and display media can be created to meet user specifications. INTRODUCTION Accurate, detailed coastal bathymetric and bottom data are vital to marine commerce, industry, and research. At sea, human lives and cargo would be in great peril without descriptive information on water depths and locations of shoals. Without this basic tool, fishing would be largely a matter of guesswork, marine construction would be nonexistent, and marine research would be paralyzed. Indeed, these data are the primary key to the hidden character of more than three-fourths of the earth's surface. Traditionally, these data have been depicted on nautical charts. Because navigators were first to use these charts, emphasis was placed on delineating shoals, rocks, reefs, and other hazards to navigation. Nautical charts published today by the National Oceanic and Atmospheric Administration's National Ocean Survey (NOS) also emphasize information of interest to the navigator. Soundings depicted on nautical charts are the shoalest of those recorded in the field. The density of the soundings collected depends upon the volume of vessel traffic and water depth in the surveyed area. Bottom samples collected are described in enough detail to enable a navigator to determine only the potential anchoring conditions. Because nautical charts are designed specifically for the navigator, they often are inadequate for the needs of the increasing number of non navigation-oriented users. A recent development in the NOS method of producing nautical charts1will make coastal bathymetric and associated charting data available to the industrial and scientific communities in forms directly applicable to their needs. In the mid-1960s, the National Ocean Survey initiated the enormous task of automating nautical chart production. This project was necessitated by the large increase in available survey data, owing to auto mated data-collection techniques and to the steadily increasing demand for new surveys and charts. As an initial step in this project, all information required to produce nautical charts was manually digitized. The digital data consists of more than 30 million soundings, bottom characteristics, and dangers to navigation.