Simplified calculation of distance measure in DP algorithm

Distance measure of point to segment is one of the determinants which affect the efficiency of DP (Douglas-Peucker) polyline simplification algorithm. Zone-divided distance measure instead of only perpendicular distance is proposed by Dan Sunday [1] to improve the deficiency of the original DP algorithm. A new efficiency zone-divided distance measure method is proposed in this paper. Firstly, a rotating coordinate is established based on the two endpoints of curve. Secondly, the new coordinate value in the rotating coordinate is computed for each point. Finally, the new coordinate values are used to divide points into three zones and to calculate distance, Manhattan distance is adopted in zone I and III, perpendicular distance in zone II. Compared with Dan Sunday’s method, the proposed method can take full advantage of the computation result of previous point. The calculation amount basically keeps for points in zone I and III, and the calculation amount reduces significantly for points in zone II which own highest proportion. Experimental results show that the proposed distance measure method can improve the efficiency of original DP algorithm.