地理空间-Java实现航迹稀释

Java实现航迹点稀释算法（Douglas - Peucker算法）的示例代码，该算法可在保证航迹整体形状变化不大的情况下减少航迹点数量：

---

import java.util.ArrayList;

import java.util.List;

 

class Point {

    double x;

    double y;

 

    public Point(double x, double y) {

        this.x = x;

        this.y = y;

    }

}

 

public class TrackThinning {

 

    public static List<Point> douglasPeucker(List<Point> points, double epsilon) {

        if (points.size() < 3) {

            return points;

        }

 

        int index = -1;

        double dmax = 0;

        int end = points.size();

        for (int i = 1; i < end - 1; i++) {

            double d = perpendicularDistance(points.get(i), points.get(0), points.get(end - 1));

            if (d > dmax) {

                index = i;

                dmax = d;

            }

        }

 

        List<Point> result = new ArrayList<>();

        if (dmax > epsilon) {

            List<Point> recursiveResult1 = douglasPeucker(points.subList(0, index + 1), epsilon);

            List<Point> recursiveResult2 = douglasPeucker(points.subList(index, points.size()), epsilon);

 

            result.addAll(recursiveResult1.subList(0, recursiveResult1.size() - 1));

            result.addAll(recursiveResult2);

        } else {

            result.add(points.get(0));

            result.add(points.get(points.size() - 1));

        }

 

        return result;

    }

 

    private static double perpendicularDistance(Point point, Point start, Point end) {

        double dx = end.x - start.x;

        double dy = end.y - start.y;

        double numerator = Math.abs((dy * point.x - dx * point.y) + (end.x * start.y - end.y * start.x));

        double denominator = Math.sqrt(dy * dy + dx * dx);

        return numerator / denominator;

    }

 

    public static void main(String[] args) {

        List<Point> points = new ArrayList<>();

        points.add(new Point(0, 0));

        points.add(new Point(1, 1));

        points.add(new Point(2, 2));

        points.add(new Point(3, 2));

        points.add(new Point(4, 3));

        points.add(new Point(5, 4));

 

        double epsilon = 0.5;

        List<Point> thinnedPoints = douglasPeucker(points, epsilon);

 

        for (Point p : thinnedPoints) {

            System.out.println("(" + p.x + ", " + p.y + ")");

        }

    }

}