The plane sweep technique is a fundamental method for solving two-dimensional geometric problems. It works with a special line called a sweepline, a vertical line sweeping the plane from left to right. It hits objects one by one as the sweepline moves. Whenever it crosses an object, a portion of the problem is solved. Therefore, it enables a two-dimensional problem to be solved in a sequence of one-dimension processing. Sweep plane technique provides a conceptually simple and efficient algorithm. Steven Fortune (1986; 1987) has developed a sweepline algorithm for constructing Thiessen polygons. This algorithm has been implemented in the Thiessen Polygon Generator. The detailed working algorithm is given as follows:

The sweepline algorithm is an efficient technique for constructing a Thiessen polygon. The computation time required for the worst case is O(nlog n). It produces a far more competent method than the naïve method and provides satisfactory performance for generating Thiessen polygons for a large number of points.