java实例 - 使用数据库实现百度地图纠偏
本文思路与代码实现完全参考了这篇文章:?gps纠偏数据库及gps纠偏算法PHP
感谢文章作者yanue的无私分享与帮助.
以下代码中所使用到的数据库文件offset.dat请到yanue的网站进行下载.
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正文代码如下:
package test.offset;import java.io.BufferedReader;import java.io.File;import java.io.FileInputStream;import java.io.InputStream;import java.io.InputStreamReader;import java.io.OutputStreamWriter;import java.net.URL;import java.net.URLConnection;import java.util.regex.Matcher;import java.util.regex.Pattern;import org.springframework.util.Assert;import sun.misc.BASE64Decoder;/** * @author 200cc * */public class OffsetReader {static final double M_PI = 3.14159265358979323846264338327950288;static final double M_E = 2.71828182845904523536028747135266250;static final String DIR = "d:\\download\\offset.dat";/** * 读取数据库offset.dat文件 * @param count 读取数据计数 * @return * @throws Exception */public static OffsetData[] readOffset(int count) throws Exception{/** dat文件结构:该文件为0.01精度校正数据,并以lng和lat递增形式组合.* 其中以8个字节为一组:* lng : 2字节经度,如12151表示121.51* lat : 2字节纬度,如3130表示31.30* x_off : 2字节地图x轴偏移像素值* y_off : 2字节地图y轴偏移像素值**/OffsetData[] datas = new OffsetData[count];File f = new File(DIR);Assert.isTrue(f.exists() && f.isFile());FileInputStream fis = new FileInputStream(f);byte[] buf = new byte[8];@SuppressWarnings("unused")int len = 0;int cnt = 0;while(-1 != (len = fis.read(buf, 0, buf.length))){if (cnt >= count) break; int lngS = byte2short(buf, 0) ; // byte[] to shortint latS = byte2short(buf, 2) ; // byte[] to shortint x = byte2short(buf, 4) ; // byte[] to shortint y = byte2short(buf, 6) ; // byte[] to shortdatas[cnt] = new OffsetData(lngS, latS, x, y);cnt++;}return datas;}public static void main(String[] args) throws Exception {OffsetData[] datas = readOffset(10);for (OffsetData data : datas){System.out.println(data);geoLatLng(data);getBaiduGeo(data.getLat() * 1.0 / 100, data.getLng() * 1.0 / 100); System.out.println("----------------------");}}/** * 获取baidu api计算的经纬 * @param lat纬度 * @param lng经度 * @throws Exception */public static void getBaiduGeo(double lat, double lng) throws Exception{//baidu APIString urlAddr = "http://api.map.baidu.com/ag/coord/convert?x=" + lng + "&y=" + lat + "&from=0&to=2&mode=1";System.out.println("request: " + urlAddr);URL url = new URL(urlAddr);URLConnection connection = url.openConnection();connection.setDoOutput(true); //将连接设置为输出模式.即发起一个http请求//URLConnection通常作为输入来使用,如下载一个web页面.//但同时也能进行输出,将数据向web页面传送.OutputStreamWriter out = new OutputStreamWriter(connection.getOutputStream(), "utf-8");out.flush();out.close();//发送成功后,获取得到服务器的响应InputStream is = connection.getInputStream();BufferedReader br = new BufferedReader(new InputStreamReader(is));String line = "";StringBuilder sb = new StringBuilder();while(null != (line = br.readLine())){sb.append(line);}System.out.println("response: " + sb.toString());//[{"error":0,"x":"NzMuNTAzMzU1MDM0NzIy","y":"MzkuMzAwMTQxODcyODM="}]Pattern p = Pattern.compile(""x":"(.+)","y":"(.+)""); //正则Matcher m = p.matcher(sb.toString());String strLng = "", strLat = "";if(m.find()){BASE64Decoder decoder = new BASE64Decoder();strLng = new String(decoder.decodeBuffer(m.group(1)));strLat = new String(decoder.decodeBuffer(m.group(2)));}else{throw new RuntimeException("");}System.out.println("baidu Geo: " + strLat + ", " + strLng);Thread.sleep(1000); //暂停一会. baidu Api有发起次数限制.}/** * byte[] 转 short * @param b * @param index * @return */public static short byte2short(byte[] b, int index){ return (short) (((b[index + 1] << 8) | b[index + 0] & 0xff));}/** * byte[] 转 float * @param b * @param index * @return */public static float getFloat(byte[] b, int index) { int l; l = b[index + 0]; l &= 0xff; l |= ((long) b[index + 1] << 8); l &= 0xffff; l |= ((long) b[index + 2] << 16); l &= 0xffffff; l |= ((long) b[index + 3] << 24); return Float.intBitsToFloat(l); }public static void geoLatLng(OffsetData data){geoLatLng(data.getLng() * 1.0 / 100, data.getLat() * 1.0 / 100, data.getOffsetPixelX(), data.getOffsetPixelY());}/** * 使用数据库计算经纬度坐标 * @param lng 实际(gps)经度 * @param lat实际(gps)纬度 * @param offsetX地图x轴偏移像素值 * @param offsetY地图y轴偏移像素值 */public static void geoLatLng(double lng, double lat, int offsetX, int offsetY){double lngPixel = lngToPixel(lng, 18) + offsetX;double latPixel = latToPixel(lat, 18) + offsetY;double mixLat = pixelToLat(latPixel, 18);double mixLng = pixelToLng(lngPixel, 18);System.out.println("calculate geo: " + mixLat + ", " + mixLng);}public static double lngToPixel(double lng, int zoom){double res = (lng + 180) * (256 << zoom) / 360;//System.out.println("lngToPixel: lng=" + lng + " --> res=" + res );return res;}public static double latToPixel(double lat , int zoom){double siny = Math.sin(lat * M_PI / 180);double y = Math.log((1 + siny) / (1 - siny));double res = (128 << zoom) * (1 - y / (2 * M_PI));//System.out.println("latToPixel: lat=" + lat + " --> res=" + res );return res;}public static double pixelToLng(double pixelX, int zoom){double res = pixelX * 360 / (256 << zoom) - 180;//System.out.println("pixelToLng: pixelX=" + pixelX + " --> res=" + res );return res;}public static double pixelToLat(double pixelY, int zoom){double y = 2 * M_PI * (1 - pixelY /(128 << zoom));double z = Math.pow(M_E , y);double siny = (z - 1) / (z + 1);double res = Math.asin(siny) * 180 / M_PI;//System.out.println("pixelToLat: pixelY=" + pixelY + " --> res=" + res );return res;}public static class OffsetData{int lng;int lat;int offsetPixelX;int offsetPixelY;public OffsetData(int lng, int lat, int x, int y){this.lng = lng;this.lat = lat;this.offsetPixelX = x;this.offsetPixelY = y;}public String toString(){return this.lng + ", " + this.lat + ", " + this.offsetPixelX + ", " + this.offsetPixelY;}public int getLng() {return lng;}public void setLng(int lng) {this.lng = lng;}public int getLat() {return lat;}public void setLat(int lat) {this.lat = lat;}public int getOffsetPixelX() {return offsetPixelX;}public void setOffsetPixelX(int offsetPixelX) {this.offsetPixelX = offsetPixelX;}public int getOffsetPixelY() {return offsetPixelY;}public void setOffsetPixelY(int offsetPixelY) {this.offsetPixelY = offsetPixelY;}}}?
运行后结果:
7350, 3930, 624, -35calculate geo: 39.30014529193229, 73.50334739685061request: http://api.map.baidu.com/ag/coord/convert?x=73.5&y=39.3&from=0&to=2&mode=1response: [{"error":0,"x":"NzMuNTAzMzU1MDM0NzIy","y":"MzkuMzAwMTQxODcyODM="}]baidu Geo: 39.30014187283, 73.503355034722----------------------7350, 3931, 624, -36calculate geo: 39.31014942177512, 73.50334739685061request: http://api.map.baidu.com/ag/coord/convert?x=73.5&y=39.31&from=0&to=2&mode=1response: [{"error":0,"x":"NzMuNTAzMzU1MzA1OTk=","y":"MzkuMzEwMTQ2NzU1NjQy"}]baidu Geo: 39.310146755642, 73.50335530599----------------------7350, 3932, 624, -37calculate geo: 39.32015355042689, 73.50334739685061request: http://api.map.baidu.com/ag/coord/convert?x=73.5&y=39.32&from=0&to=2&mode=1response: [{"error":0,"x":"NzMuNTAzMzU1NTc3MjU3","y":"MzkuMzIwMTUxMzY3MTg3"}]baidu Geo: 39.320151367187, 73.503355577257----------------------7350, 3933, 625, -38calculate geo: 39.33015767788718, 73.50335276126864request: http://api.map.baidu.com/ag/coord/convert?x=73.5&y=39.33&from=0&to=2&mode=1response: [{"error":0,"x":"NzMuNTAzMzU2MTE5Nzky","y":"MzkuMzMwMTU1NzA3NDY1"}]baidu Geo: 39.330155707465, 73.503356119792----------------------7350, 3934, 625, -39calculate geo: 39.34016180415566, 73.50335276126864request: http://api.map.baidu.com/ag/coord/convert?x=73.5&y=39.34&from=0&to=2&mode=1response: [{"error":0,"x":"NzMuNTAzMzU2MzkxMDU5","y":"MzkuMzQwMTYwMzE5MDE="}]baidu Geo: 39.34016031901, 73.503356391059----------------------7350, 3935, 625, -40calculate geo: 39.350165929231935, 73.50335276126864request: http://api.map.baidu.com/ag/coord/convert?x=73.5&y=39.35&from=0&to=2&mode=1response: [{"error":0,"x":"NzMuNTAzMzU2NjYyMzI2","y":"MzkuMzUwMTY0NjU5Mjg4"}]baidu Geo: 39.350164659288, 73.503356662326----------------------7350, 3936, 625, -41calculate geo: 39.36017005311557, 73.50335276126864request: http://api.map.baidu.com/ag/coord/convert?x=73.5&y=39.36&from=0&to=2&mode=1response: [{"error":0,"x":"NzMuNTAzMzU2OTMzNTk0","y":"MzkuMzYwMTY4OTk5NTY2"}]baidu Geo: 39.360168999566, 73.503356933594----------------------7350, 3937, 625, -42calculate geo: 39.37017417580627, 73.50335276126864request: http://api.map.baidu.com/ag/coord/convert?x=73.5&y=39.37&from=0&to=2&mode=1response: [{"error":0,"x":"NzMuNTAzMzU3NDc2MTI4","y":"MzkuMzcwMTczMDY4NTc2"}]baidu Geo: 39.370173068576, 73.503357476128----------------------7350, 3938, 625, -43calculate geo: 39.380178297303594, 73.50335276126864request: http://api.map.baidu.com/ag/coord/convert?x=73.5&y=39.38&from=0&to=2&mode=1response: [{"error":0,"x":"NzMuNTAzMzU3NzQ3Mzk2","y":"MzkuMzgwMTc3MTM3NTg3"}]baidu Geo: 39.380177137587, 73.503357747396----------------------7351, 3930, 616, -28calculate geo: 39.30011623356995, 73.51330448150634request: http://api.map.baidu.com/ag/coord/convert?x=73.51&y=39.3&from=0&to=2&mode=1response: [{"error":0,"x":"NzMuNTEzMzEyMTc0NDc5","y":"MzkuMzAwMTEyMDMzNDI="}]baidu Geo: 39.30011203342, 73.513312174479----------------------?
总结:
从运行结果可以看到,使用数据库计算后的结果,与baidu返回的数据间的差值大约在0.0001左右.误差值还是挺大的.- -b.
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本人能力有限,代码中肯定还存在错误,恳请诸位指正.
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此外还衍生出一个问题:?我在网上查到
Q：百度坐标为何有偏移？A：国际经纬度坐标标准为WGS-84,国内必须至少使用国测局制定的GCJ-02,对地理位置进行首次加密。百度坐标在此基础上，进行了BD-09二次加密措施,更加保护了个人隐私。...?使用这个offset.dat数据文件,计算得到的值居然能粗略拟合百度的二次火星坐标,我自己都觉得这是不是有些不可思议了?