The geographic distribution of the tidal datums were determined by a fully calibrated tide model or by spatial interpolation of water levels computed from tide gauge measurements. High-resolution third party bathymetric and topographic data, as well as shoreline data processed from airborne and satellite remote sensing sources, were vertically referenced before being incorporated into the DEM. Where data were sufficiently dense, attempts were made to produce a higher-resolution "shoreline zone" in the DEM, from which internally consistent "shorelines" can be generated by moving the water level in the DEM to desired tidal datum heights. The Bathy-Topo DEM and shorelines not only solve the problem of inconsistency between NOS and USGS products that has caused difficulty for coastal managers, they also provide standard geospatial data for multiple applications.

This is a first step toward the development of a mutually agreed upon "national shoreline". For NOAA and USGS it is potentially the beginning of a new way of doing business with each other that reduces the duplication of effort and better meets the needs of state and county agencies. Applications benefitting from the Bathy-Topo DEM include: improved hurricane evacuation plans (based on improved storm surge modeling); improved and consistent geospatial data for county planners; better located habitat restoration projects; and detailed electronic nautical charts, to name just a few. Also important, this project promotes metadata standards and the reliable use of data from many different sources. This project should be viewed as a "demonstration" in the broadest sense, and includes the development of promising new technical and scientific techniques.

Marine and terrestrial spatial data produced with standard metadata, as well as visualizations of the resulting DEM and shoreline for Tampa Bay are available on-line (Spatial Data and Visualizations), and on CD-ROM.

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