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the rapidly-emerging electronic chart systems can help avoid 

 accidents such as the recent EXXON VALDEZ disaster. Real-time 

 water level and current data are needed for safe navigation. In 

 the air, a new generation of navigation data sets will be 

 required for the developing air traffic control Advanced 

 Automation System and the new microwave or satellite-based 

 instrument landing systems. On land, sea, and air the existing 

 coordinate reference system must be renovated to provide the 

 higher accuracy, and different accessibility needed for space- 

 based Global Positioning System. 



Finally, there is an increasing demand for consistent, compatible 

 data bases for engineering and scientific purposes. The annual 

 national public expenditures for spatial data collection, 

 maintenance, and manipulation are estimated to be about 

 $7 billion. Development of the needed geographic data is 

 invariably the largest cost factor in the increasing use of 

 Geographic Information Systems (GIS) . This investment has 

 limited value if the data are not based on accurate, compatible 

 coordinates. Convenient, quick, and inexpensive access to a 

 unified, consistent reference framework — the National Spatial 

 Reference System — is necessary. The fundamental layers of a 

 coastal zone GIS, tied to this framework and derived from the 

 NCAA charting data base, must be available to a broad and diverse 

 user community. 



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