Digitized global land-sea map and access software

A computer-efficient global data file, which contains digitized information that enables identification of a given latitude/longitude defined point as over land or over water, was generated from a data base which defines the world's shoreline. The method used in the generation of this land-sea boundary data map and its data structure are discussed. The data file was originally generated on a Control Data Corporation(CDC) computer, but it has been transported to other computer systems, includingIBM, DEC/VAX, UNIVAC and Cray computers. The land-sea boundary map also includes information on islands and inland lakes. The resolution of this map is 5′×5′ or an equivalent of9 km square surface blocks at the equator. The software to access this data base is structured to be easily transportable to different computers. This data base was used in the generation of the Seasat Geophysical Data Record(GDR) to identify whether a spaceborne radar altimeter measurement was over-land or over-ocean.