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A Geospatial Framework for the Coastal Zone: National Needs for Coastal Mapping and Charting
less transition from onshore to offshore, including clarification of offshore boundary definitions and a framework to allow consistent shoreline definitions;
Increased collection and availability of primary reference frame and thematic data, including shallow-water bathymetry, acoustic and satellite imagery of the seafloor, bottom type, habitat distribution and classification standards, land use, land cover, and coastal change data.
Easy access to up-to-date digital, geospatial data, imagery, and mapping products;
Compatibility among data formats, or standards and transformation protocols that allow easy data exchange, and a means to evaluate the accuracy of geospatial data; and
Increased inter- and intra-agency communication, cooperation, and coordination.
Addressing these critical issues, which are described in more detail below, will provide the basic reference frame, source data, and tools necessary to create the wide range of derivative products needed to efficiently and effectively manage the coastal zone.
A Consistent Spatial Framework
Any discussion of the coastal zone must acknowledge the unique aspects of this dynamic region. Coastal zone data collection and mapping present a special challenge because most coastal processes are both continuous across the land-sea interface and are subject to constant natural and anthropogenic change. The historical divisions between topographic mapping techniques onshore and bathymetric charting approaches offshore, and the fundamentally different vertical reference frames used, have resulted in a serious incompatibility between existing maps and charts. In particular, offshore features must be measured with respect to the constantly changing tide level, adding considerable complexity to coastal zone mapping and creating enormous difficulties in seamlessly merging onshore and offshore data. A multiplicity of tidal datums, and their dynamic nature, has produced ambiguity in the definition of the shoreline, creating considerable confusion and difficulty in integrating coastal zone studies and management. Additionally, the ever-shifting land-water interface poses significant logistical challenges for mapping. Shallow water, waves, turbidity, and longshore currents all contribute to the difficulty of operating vessels and equipment accurately and safely. These issues are all reflected in the unified call from the user community for a consistent spatial framework that allows a seamless transition from onshore to offshore.