Java是目前比较受欢迎的开发语言了，它简单安全等特点让其在很多企业中应用，同时我们也可以使用java开发很多应用，那java电子地图如何实现?下面来我们就来给大家讲解一下。
1、首先弄明白几种在线地图的坐标系;
(1)天地图：CGCS2000，2000国家大地坐标系;我们其实很多时候直接用WGS84的坐标来代替CGCS2000坐标。因为CGCS2000的定义与WGS84实质一样。采用的参考椭球非常接近。扁率差异引起椭球面上的纬度和高度变化最大达0.1mm。当前测量精度范围内，可以忽略这点差异。可以说两者相容至cm级水平，但若一点的坐标精度达不到cm水平，则不认为CGCS2000和WGS84的坐标是相容的。
(2)百度地图：bd09II坐标。首先了解一下火星坐标，它是在国际标准坐标WGS-84上进行的一次加密，由于国内的电子地图都要至少使用火星坐标进行一次加密，百度直接就任性一些，直接自己又研究了一套加密算法，来了个二次加密，这就是我们所熟知的百度坐标(BD-09)。
(3)高德地图：gcj02坐标，也称为火星坐标。火星坐标是国家测绘局为了国家安全在原始坐标的基础上进行偏移得到的坐标，基本国内的电子地图、导航设备都是采用的这一坐标系或在这一坐标的基础上进行二次加密得到的。
(4)一些注意点：非专业人士，对于墨卡托投影坐标和经纬度坐标可以理解为一个是平面坐标一个是球面坐标。还有用wgs84坐标系的一些地图，比如： osm、谷歌、arcgisonline等。
2、几种坐标系之间的转换算法;
(1)百度坐标转火星坐标：
var x_pi = 3.14159265358979324 * 3000.0 / 180.0;
function baiduTomars(baidu_point)
{
var mars_point = {
lon: 0
, lat: 0
};
var x = baidu_point.lon - 0.0065;
var y = baidu_point.lat - 0.006;
var z = Math.sqrt(x * x + y * y) - 0.00002 * Math.sin(y * x_pi);
var theta = Math.atan2(y, x) - 0.000003 * Math.cos(x * x_pi);
mars_point.lon = z * Math.cos(theta);
mars_point.lat = z * Math.sin(theta);
return mars_point;
}(2)火星坐标转百度坐标：
x_pi = 3.14159265358979324 * 3000.0 / 180.0;
function marsTobaidu(mars_point)
{
var baidu_point = {
lon: 0
, lat: 0
};
var x = mars_point.lon;
var y = mars_point.lat;
var z = Math.sqrt(x * x + y * y) + 0.00002 * Math.sin(y * x_pi);
var theta = Math.atan2(y, x) + 0.000003 * Math.cos(x * x_pi);
baidu_point.lon = z * Math.cos(theta) + 0.0065;
baidu_point.lat = z * Math.sin(theta) + 0.006;
return baidu_point;
}(3)地球坐标系(WGS-84)转火星坐标系(GCJ)：
var pi = 3.14159265358979324;
var a = 6378245.0;
var ee = 0.00669342162296594323;
/*判断是否在国内，不在国内则不做偏移*/
function outOfChina(lon, lat)
{
if ((lon < 72.004 || lon > 137.8347) && (lat < 0.8293 || lat > 55.8271))
{
return true;
}
else
{
return false;
}
}
function transformLat(x, y)
{
var ret = -100.0 + 2.0 * x + 3.0 * y + 0.2 * y * y + 0.1 * x * y + 0.2 * Math.sqrt(Math.abs(x));
ret += (20.0 * Math.sin(6.0 * x * pi) + 20.0 * Math.sin(2.0 * x * pi)) * 2.0 / 3.0;
ret += (20.0 * Math.sin(y * pi) + 40.0 * Math.sin(y / 3.0 * pi)) * 2.0 / 3.0;
ret += (160.0 * Math.sin(y / 12.0 * pi) + 320 * Math.sin(y * pi / 30.0)) * 2.0 / 3.0;
return ret;
}
function transformLon(x, y)
{
var ret = 300.0 + x + 2.0 * y + 0.1 * x * x + 0.1 * x * y + 0.1 * Math.sqrt(Math.abs(x));
ret += (20.0 * Math.sin(6.0 * x * pi) + 20.0 * Math.sin(2.0 * x * pi)) * 2.0 / 3.0;
ret += (20.0 * Math.sin(x * pi) + 40.0 * Math.sin(x / 3.0 * pi)) * 2.0 / 3.0;
ret += (150.0 * Math.sin(x / 12.0 * pi) + 300.0 * Math.sin(x / 30.0 * pi)) * 2.0 / 3.0;
return ret;
}
function transform(wgLat, wgLon)
{
var mars_point = {
lon: 0
, lat: 0
};
if (outOfChina(wgLat, wgLon))
{
mars_point.lat = wgLat;
mars_point.lon = wgLon;
return;
}
var dLat = transformLat(wgLon - 105.0, wgLat - 35.0);
var dLon = transformLon(wgLon - 105.0, wgLat - 35.0);
var radLat = wgLat / 180.0 * pi;
var magic = Math.sin(radLat);
magic = 1 - ee * magic * magic;
var sqrtMagic = Math.sqrt(magic);
dLat = (dLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * pi);
dLon = (dLon * 180.0) / (a / sqrtMagic * Math.cos(radLat) * pi);
mars_point.lat = wgLat + dLat;
mars_point.lon = wgLon + dLon;
return mars_point
}(4)火星坐标系GCJ02转地球坐标系WGS84：
var PI = 3.14159265358979324;
function transformGCJ2WGS(gcjLat, gcjLon)
{
let d = delta(gcjLat, gcjLon)
return {
'lat': gcjLat - d.lat
, 'lon': gcjLon - d.lon
}
}
function delta(lat, lon)
{
let a = 6378245.0 // a: 卫星椭球坐标投影到平面地图坐标系的投影因子。
let ee = 0.00669342162296594323 // ee: 椭球的偏心率。
let dLat = transformLat(lon - 105.0, lat - 35.0)
let dLon = transformLon(lon - 105.0, lat - 35.0)
let radLat = lat / 180.0 * PI
let magic = Math.sin(radLat)
magic = 1 - ee * magic * magic
let sqrtMagic = Math.sqrt(magic)
dLat = (dLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * PI)
dLon = (dLon * 180.0) / (a / sqrtMagic * Math.cos(radLat) * PI)
return {
'lat': dLat
, 'lon': dLon
}
}
function transformLat(x, y)
{
let ret = -100.0 + 2.0 * x + 3.0 * y + 0.2 * y * y + 0.1 * x * y + 0.2 * Math.sqrt(Math.abs(x))
ret += (20.0 * Math.sin(6.0 * x * PI) + 20.0 * Math.sin(2.0 * x * PI)) * 2.0 / 3.0
ret += (20.0 * Math.sin(y * PI) + 40.0 * Math.sin(y / 3.0 * PI)) * 2.0 / 3.0
ret += (160.0 * Math.sin(y / 12.0 * PI) + 320 * Math.sin(y * PI / 30.0)) * 2.0 / 3.0
return ret
}
function transformLon(x, y)
{
let ret = 300.0 + x + 2.0 * y + 0.1 * x * x + 0.1 * x * y + 0.1 * Math.sqrt(Math.abs(x))
ret += (20.0 * Math.sin(6.0 * x * PI) + 20.0 * Math.sin(2.0 * x * PI)) * 2.0 / 3.0
ret += (20.0 * Math.sin(x * PI) + 40.0 * Math.sin(x / 3.0 * PI)) * 2.0 / 3.0
ret += (150.0 * Math.sin(x / 12.0 * PI) + 300.0 * Math.sin(x / 30.0 * PI)) * 2.0 / 3.0
return ret
}(5)百度经纬度坐标转百度墨卡托坐标：
var LLBAND = [75, 60, 45, 30, 15, 0]
var LL2MC = [
[-0.0015702102444, 111320.7020616939, 1704480524535203, -10338987376042340, 26112667856603880, -35149669176653700, 26595700718403920, -10725012454188240, 1800819912950474, 82.5]
, [0.0008277824516172526, 111320.7020463578, 647795574.6671607, -4082003173.641316, 10774905663.51142, -15171875531.51559, 12053065338.62167, -5124939663.577472, 913311935.9512032, 67.5]
, [0.00337398766765, 111320.7020202162, 4481351.045890365, -23393751.19931662, 79682215.47186455, -115964993.2797253, 97236711.15602145, -43661946.33752821, 8477230.501135234, 52.5]
, [0.00220636496208, 111320.7020209128, 51751.86112841131, 3796837.749470245, 992013.7397791013, -1221952.21711287, 1340652.697009075, -620943.6990984312, 144416.9293806241, 37.5]
, [-0.0003441963504368392, 111320.7020576856, 278.2353980772752, 2485758.690035394, 6070.750963243378, 54821.18345352118, 9540.606633304236, -2710.55326746645, 1405.483844121726, 22.5]
, [-0.0003218135878613132, 111320.7020701615, 0.00369383431289, 823725.6402795718, 0.46104986909093, 2351.343141331292, 1.58060784298199, 8.77738589078284, 0.37238884252424, 7.45]
]
function getRange(cC, cB, T)
{
if (cB != null)
{
cC = Math.max(cC, cB);
}
if (T != null)
{
cC = Math.min(cC, T);
}
return cC;
}
function getLoop(cC, cB, T)
{
while (cC > T)
{
cC -= T - cB;
}
while (cC < cB)
{
cC += T - cB;
}
return cC;
}
function convertor(cC, cD)
{
if (!cC || !cD)
{
return null;
}
let T = cD[0] + cD[1] * Math.abs(cC.x);
const cB = Math.abs(cC.y) / cD[9];
let cE = cD[2] + cD[3] * cB + cD[4] * cB * cB +
cD[5] * cB * cB * cB + cD[6] * cB * cB * cB * cB +
cD[7] * cB * cB * cB * cB * cB +
cD[8] * cB * cB * cB * cB * cB * cB;
T *= (cC.x < 0 ? -1 : 1);
cE *= (cC.y < 0 ? -1 : 1);
return [T, cE];
}
function convertLL2MC(T)
{
let cD, cC, len;
T.x = getLoop(T.x, -180, 180);
T.y = getRange(T.y, -74, 74);
const cB = T;
for (cC = 0, len = LLBAND.length; cC < len; cC++)
{
if (cB.y >= LLBAND[cC])
{
cD = LL2MC[cC];
break;
}
}
if (!cD)
{
for (cC = LLBAND.length - 1; cC >= 0; cC--)
{
if (cB.y <= -LLBAND[cC])
{
cD = LL2MC[cC];
break;
}
}
}
const cE = convertor(T, cD);
return cE;
}(6)百度墨卡托坐标转百度经纬度坐标：
var MCBAND = [12890594.86, 8362377.87, 5591021, 3481989.83, 1678043.12, 0]
var 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]
]
function convertor(cC, cD)
{
if (!cC || !cD)
{
return null;
}
let T = cD[0] + cD[1] * Math.abs(cC.x);
const cB = Math.abs(cC.y) / cD[9];
let cE = cD[2] + cD[3] * cB + cD[4] * cB * cB +
cD[5] * cB * cB * cB + cD[6] * cB * cB * cB * cB +
cD[7] * cB * cB * cB * cB * cB +
cD[8] * cB * cB * cB * cB * cB * cB;
T *= (cC.x < 0 ? -1 : 1);
cE *= (cC.y < 0 ? -1 : 1);
return [T, cE];
}
function convertMC2LL(cB)
{
const cC = {
x: Math.abs(cB.x)
, y: Math.abs(cB.y)
};
let cE;
for (let cD = 0, len = MCBAND.length; cD < len; cD++)
{
if (cC.y >= MCBAND[cD])
{
cE = MC2LL[cD];
break;
}
}
const T = convertor(cB, cE);
return T;
}(7)经纬度坐标转墨卡托坐标(不太精确)：
function lonlatTomercator(lonlat)
{
var mercator = {
x: 0
, y: 0
};
var x = lonlat.x * 20037508.34 / 180;
var y = Math.log(Math.tan((90 + lonlat.y) * Math.PI / 360)) / (Math.PI / 180);
y = y * 20037508.34 / 180;
mercator.x = x;
mercator.y = y;
return mercator;
}(8)墨卡托坐标转经纬度坐标(不太精确)：
function mercatorTolonlat(mercator)
{
var lonlat = {
x: 0
, y: 0
};
var x = mercator.x / 20037508.34 * 180;
var y = mercator.y / 20037508.34 * 180;
y = 180 / Math.PI * (2 * Math.atan(Math.exp(y * Math.PI / 180)) - Math.PI / 2);
lonlat.x = x;
lonlat.y = y;
return lonlat;
}这样一些常用的地图坐标系之间就可以相互转换了，其实实现这样的功能还是比较复杂的，但是只要我们了解其逻辑与算法，也就没有那么难!最后大家如果想要了解更多java实例知识，敬请关注奇Q工具网。
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