背景：某项目做区域监控，需要内置某些区域的电子围栏。

方案：利用某度接口中墨卡托投影值，进行经纬度转换，入库保存后，让前端获取。

前置数据：区域文案名清单

接口1:  查询某区域的uid

http://api.map.baidu.com/place/v2/search?output=json&scope=2&q=" + area + "&region=" + city + "&ak=" + ak

area：某区域文案在地图上的文案名

city：该区域所在城市

ak: token

接口2:  获取墨卡托值

http://map.baidu.com/?reqflag=pcmap&coord_type=3&from=webmap&qt=ext&ext_ver=new&l=18&uid=" + uid

uid：接口1获取

墨卡托值是接口2返回值里的geo字段值

墨卡托算法(经纬度转换)

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

public class MocatorUtils {

private static Double[] MCBAND = {12890594.86, 8362377.87, 5591021d, 3481989.83, 1678043.12, 0d};

private static Double[][] MC2LL = {{1.410526172116255e-8, 0.00000898305509648872, -1.9939833816331, 200.9824383106796, -187.2403703815547, 91.6087516669843, -23.38765649603339, 2.57121317296198, -0.03801003308653, 17337981.2}, {-7.435856389565537e-9, 0.000008983055097726239, -0.78625201886289, 96.32687599759846, -1.85204757529826, -59.36935905485877, 47.40033549296737, -16.50741931063887, 2.28786674699375, 10260144.86}, {-3.030883460898826e-8, 0.00000898305509983578, 0.30071316287616, 59.74293618442277, 7.357984074871, -25.38371002664745, 13.45380521110908, -3.29883767235584, 0.32710905363475, 6856817.37}, {-1.981981304930552e-8, 0.000008983055099779535, 0.03278182852591, 40.31678527705744, 0.65659298677277, -4.44255534477492, 0.85341911805263, 0.12923347998204, -0.04625736007561, 4482777.06}, {3.09191371068437e-9, 0.000008983055096812155, 0.00006995724062, 23.10934304144901, -0.00023663490511, -0.6321817810242, -0.00663494467273, 0.03430082397953, -0.00466043876332, 2555164.4}, {2.890871144776878e-9, 0.000008983055095805407, -3.068298e-8, 7.47137025468032, -0.00000353937994, -0.02145144861037, -0.00001234426596, 0.00010322952773, -0.00000323890364, 826088.5}};

public static List parseJeo(String mocator) {

List mocatorList = new ArrayList();

if (null == mocator) return null;

/* 拆分数据 */

String[] geos = mocator.split("\\|");

int n = Integer.parseInt(geos[0]);

String center = geos[1];

String polylineMoca = geos[2]; //墨卡托坐标

String[] plm = polylineMoca.split("\\;");

/* 获取墨卡托边界 */

String geo = null;

if (n == 4) {

for (int i = 0; i < plm.length; i++) {

String[] geoPaths = plm[i].split("\\-");

if (geoPaths[0].equals("1")) {

geo = geoPaths[1];

}

}

}

if(n == 3){

geo = plm[0];

}

// 墨卡托坐标解析

String[] geoPolyline = geo.split("\\,");

for (int i = 0; i < geoPolyline.length; i += 2) {

mocatorList.add(geoPolyline[i] + "#" + geoPolyline[i + 1]);

}

return mocatorList;

}

/**

* @param mocator

* @return lat lng

*/

public static List calCoords(String mocator, boolean transfer284) {

List mocatorList = parseJeo(mocator);

List coords = new ArrayList<>();

// 封装板块边界

for (int i = 0; i < mocatorList.size(); i++) {

String[] coordinate = mocatorList.get(i).split("\\#");

// 墨卡托坐标转换为百度经纬度坐标

Map location = convertMC2LL(Double.parseDouble(coordinate[0]), Double.parseDouble(coordinate[1]));

Double lng = location.get("lng");

Double lat = location.get("lat");

double[] aa;

if (transfer284) {

//百度09坐标系转84坐标系

aa = GpsUtil.bd09Togps84(lat, lng);

} else {

aa = new double[]{lat, lng};

}

coords.add(aa);

}

return coords;

}

/**

* 墨卡托坐标转经纬度坐标

*

* @param x

* @param y

* @return

*/

public static Map convertMC2LL(Double x, Double y) {

Double[] cF = null;

x = Math.abs(x);

y = Math.abs(y);

for (int cE = 0; cE < MCBAND.length; cE++) {

if (y >= MCBAND[cE]) {

cF = MC2LL[cE];

break;

}

}

Map location = converter(x, y, cF);

location.put("lng", location.get("x"));

location.remove("x");

location.put("lat", location.get("y"));

location.remove("y");

return location;

}

private static Map converter(Double x, Double y, Double[] cE) {

Double xTemp = cE[0] + cE[1] * Math.abs(x);

Double cC = Math.abs(y) / cE[9];

Double yTemp = cE[2] + cE[3] * cC + cE[4] * cC * cC + cE[5] * cC * cC * cC + cE[6] * cC * cC * cC * cC + cE[7] * cC * cC * cC * cC * cC + cE[8] * cC * cC * cC * cC * cC * cC;

xTemp *= (x < 0 ? -1 : 1);

yTemp *= (y < 0 ? -1 : 1);

Map location = new HashMap();

location.put("x", xTemp);

location.put("y", yTemp);

return location;

}

}