Territorial sea belt data preparation manner and the Territorial sea belt data preparation device and

摘要

PROBLEM TO BE SOLVED: To prepare computer readable territorial shoreline data by approximating the territory of Japan with plural closed polygons and calculating latitude/longitude on a circumference with the radius of prescribed sea miles from respective apexes in order tracing the closed polygons. ;SOLUTION: With the respective points of shoreline data C1 as a center, the value of latitude/longitude on the circumference with the radius of three sea miles is calculated for each fixed angle. This operation is performed concerning all the shoreline data C1 so that three-sea miles redundant data C2 having the information of latitude/ longitude at each point can be obtained. From three-sea miles redundant data C2 provided from the points of the shoreline data C1, points existent less than three sea miles from the other points are erased. This operation is performed to all the shoreline data C1 so that points on the circumference of three sea miles can be obtained. Next, a semi-straight line is drawn right to the north as a point on the circumference of three sea miles as a base point. Corresponding to whether the number of times for this semi-straight line to cross the shoreline is odd or even, points within the territory or on the sea are discriminated and only the points on the sea are preserved in a data preserving means.;COPYRIGHT: (C)2000,JPO