这篇文章主要介绍了Java编程如何实现轨迹压缩算法开放窗口，具有一定借鉴价值，感兴趣的朋友可以参考下，希望大家阅读完这篇文章之后大有收获，下面让小编带着大家一起了解一下。
轨迹压缩算法
场景描述
给定一个GPS数据记录文件，每条记录包含经度和维度两个坐标字段，根据距离阈值压缩记录，将过滤后的所有记录的经纬度坐标构成一条轨迹
算法描述
这种算法的用处还是相当广泛的。
轨迹压缩算法分为两大类，分别是无损压缩和有损压缩，无损压缩算法主要包括哈夫曼编码，有损压缩算法又分为批处理方式和在线数据压缩方式，其中批处理方式又包括DP（Douglas-Peucker）算法、TD-TR（Top-Down Time-Ratio）算法和Bellman算法，在线数据压缩方式又包括滑动窗口、开放窗口、基于安全区域的方法等。
大家也可参考这篇文章：《Java编程实现轨迹压缩之Douglas-Peucker算法详细代码》
代码实现
import java.awt.Color;import java.awt.Graphics;import java.awt.Point;import java.awt.Toolkit;import java.io.BufferedReader;import java.io.File;import java.io.FileInputStream;import java.io.InputStreamReader;import java.io.RandomAccessFile;import java.text.DecimalFormat;import java.util.ArrayList;import java.util.Iterator;import javax.swing.JFrame;import javax.swing.JPanel;public class TrajectoryCom {public static void main(String[] args) throws Exception{//阈值定义double maxDistanceError = 30;//存放从文件读取的位置点的信息列表ArrayList<enpoint> ENPList = new ArrayList<enpoint>();//源数据文件的地址 建立文件对象//这里是需要更改的地方 改你源文件的存放地址 记住如果地址中含"\",记得再加一个"\"，原因"\"是转义符号 //这里可以写成C:/Users/Administrator/Desktop/11.6/2007-10-14-GPS.logFile sourceFile = new File("./2007-10-14-GPS.log");//调用文件读取函数 读取文件数据ENPList = getENPointFromFile(sourceFile);//这里是测试 有没有读到里面 看看列表里的数据个数 交作业的时候记得注释掉System.out.println(ENPList.size());//存放目标点的集合ArrayList<enpoint> rePointList = new ArrayList<enpoint>();rePointList = openWindowTra(ENPList,maxDistanceError);System.out.println(rePointList.size());File targetFile = new File("./2007-10-14-GPSResult.log");writeTestPointToFile(targetFile,rePointList);double cpL = (double)rePointList.size() / (double)ENPList.size() * 100;DecimalFormat df = new DecimalFormat("0.000000");System.out.println("压缩率："+ df.format(cpL) + "%");double aveDisErr = getMeanDistError(ENPList,rePointList);System.out.println(aveDisErr);//generateImage(ENPList,rePointList);}public static ArrayList<enpoint> getENPointFromFile(File fGPS)throws Exception{ArrayList<enpoint> pGPSArray = new ArrayList<enpoint>();if(fGPS.exists()&&fGPS.isFile()){InputStreamReader read = new InputStreamReader(new FileInputStream(fGPS));//输入流初始化BufferedReader bReader = new BufferedReader(read);//缓存读取初始化String str;String[] strGPS;int i = 0;while((str = bReader.readLine())!=null){//每次读一行strGPS = str.split(" ");ENPoint p = new ENPoint();p.id = i;i++;p.pe = (dfTodu(strGPS[3]));p.pn = (dfTodu(strGPS[5]));pGPSArray.add(p);}bReader.close();}return pGPSArray;}public static double dfTodu(String str){int indexD = str.indexOf('.');//获取 . 字符所在的位置String strM = str.substring(0,indexD-2);//整数部分String strN = str.substring(indexD-2);//小数部分double d = double.parsedouble(strM)+double.parsedouble(strN)/60;return d;}public static ArrayList<enpoint> openWindowTra(ArrayList<enpoint> sourceList,double maxDis){ArrayList<enpoint> targetList = new ArrayList<enpoint>();//定义初始点位置 最开始初始点位置为0 int startPoint = 0;//定义浮动点位置 最开始初始点位置2int floatPoint = 2;//定义当前轨迹点位置 最开始初始点位置为1int nowPoint = 1;int len = sourceList.size();//存放所有窗口内的点的信息集合 ArrayList<enpoint> listPoint = new ArrayList<enpoint>();listPoint.add(sourceList.get(nowPoint));//浮动点位置决定循环while(true){//标志 用来控制判断是否进行窗口内轨迹点更新Boolean flag = false;//计算并判断窗口内所有点和投影点的距离是否大于阈值for (ENPoint point:listPoint){double disOfTwo = getDistance(sourceList.get(startPoint),sourceList.get(floatPoint),point);if(disOfTwo >= 30){flag = true;break;}}if(flag){//窗口内点距离都大于阈值//初始点加到目标列表targetList.add(sourceList.get(startPoint));//初始点变化startPoint = floatPoint - 1;//浮动点变化floatPoint += 1;if(floatPoint >= len){targetList.add(sourceList.get(floatPoint-1));break;}//窗口内点变化listPoint.clear();//System.out.println(listPoint.size());listPoint.add(sourceList.get(startPoint+1));} else{//距离小于阈值的情况//初始点不变//当前窗口集合加入当前浮动点listPoint.add(sourceList.get(floatPoint));//浮动点后移一位floatPoint += 1;//如果浮动点是终点 且当前窗口点距离都小于阈值 就直接忽略窗口点 直接将终点加入目标点集合if(floatPoint >= len){targetList.add(sourceList.get(startPoint));targetList.add(sourceList.get(floatPoint-1));break;}}flag = false;}return targetList;}public static double getDistance(ENPoint A,ENPoint B,ENPoint C){double distance = 0;double a = Math.abs(geoDist(A,B));double b = Math.abs(geoDist(B,C));double c = Math.abs(geoDist(A,C));double p = (a + b + c)/2.0;double s = Math.sqrt(p * (p-a) * (p-b) * (p-c));distance = s * 2.0 / a;return distance;}public static double geoDist(ENPoint pA,ENPoint pB){double radLat1 = Rad(pA.pn);double radLat2 = Rad(pB.pn);double delta_lon = Rad(pB.pe - pA.pe);double top_1 = Math.cos(radLat2) * Math.sin(delta_lon);double top_2 = Math.cos(radLat1) * Math.sin(radLat2) - Math.sin(radLat1) * Math.cos(radLat2) * Math.cos(delta_lon);double top = Math.sqrt(top_1 * top_1 + top_2 * top_2);double bottom = Math.sin(radLat1) * Math.sin(radLat2) + Math.cos(radLat1) * Math.cos(radLat2) * Math.cos(delta_lon);double delta_sigma = Math.atan2(top, bottom);double distance = delta_sigma * 6378137.0;return distance;}public static double Rad(double d){return d * Math.PI / 180.0;}public static void writeTestPointToFile(File outGPSFile,ArrayList<enpoint> pGPSPointFilter)throws Exception{Iterator<enpoint> iFilter = pGPSPointFilter.iterator();RandomAccessFile rFilter = new RandomAccessFile(outGPSFile,"rw");while(iFilter.hasNext()){ENPoint p = iFilter.next();String sFilter = p.getResultString();byte[] bFilter = sFilter.getBytes();rFilter.write(bFilter);}rFilter.close();}public static double getMeanDistError(ArrayList<enpoint> pGPSArray,ArrayList<enpoint> pGPSArrayRe){double sumDist = 0.0;for (int i=1;i<pgpsarrayre.size();i++){double="" end="pGPSArrayRe.get(i).id;" int="" j="start+1;j<end;j++){" meandist="sumDist/(pGPSArray.size());" pre="" return="" start="pGPSArrayRe.get(i-1).id;" sumdist=""><pre class="brush:java;">import java.text.DecimalFormat;public class ENPoint implements Comparable<enpoint>{ public int id;//点IDpublic double pe;//经度public double pn;//维度public ENPoint(){}//空构造函数public String toString(){return this.id+"#"+this.pn+","+this.pe;}public String getResultString(){DecimalFormat df = new DecimalFormat("0.000000");return this.id+"#"+df.format(this.pe)+","+df.format(this.pn)+" \n";}@Override public int compareTo(ENPoint other) {if(this.id<other.id) else="" return="" this.id="">other.id) return 1; else return 0;}}感谢你能够认真阅读完这篇文章，希望小编分享的“Java编程如何实现轨迹压缩算法开放窗口”这篇文章对大家有帮助，同时也希望大家多多支持编程网，关注编程网行业资讯频道，更多相关知识等着你来学习!
