1.传入两个经纬度坐标，计算出两个坐标之间的角度，范围是0-360。
// 计算方位角,正北向为0度，以顺时针方向递增
private double computeAzimuth(LatLng la1, LatLng la2) {
double lat1 = la1.latitude, lon1 = la1.longitude, lat2 = la2.latitude,
lon2 = la2.longitude;
double result = 0.0;
int ilat1 = (int) (0.50 + lat1 * 360000.0);
int ilat2 = (int) (0.50 + lat2 * 360000.0);
int ilon1 = (int) (0.50 + lon1 * 360000.0);
int ilon2 = (int) (0.50 + lon2 * 360000.0);
lat1 = Math.toRadians(lat1);
lon1 = Math.toRadians(lon1);
lat2 = Math.toRadians(lat2);
lon2 = Math.toRadians(lon2);
if ((ilat1 == ilat2) && (ilon1 == ilon2)) {
return result;
} else if (ilon1 == ilon2) {
if (ilat1 > ilat2)
result = 180.0;
} else {
double c = Math
.acos(Math.sin(lat2) * Math.sin(lat1) + Math.cos(lat2)
* Math.cos(lat1) * Math.cos((lon2 - lon1)));
double A = Math.asin(Math.cos(lat2) * Math.sin((lon2 - lon1))
/ Math.sin(c));
result = Math.toDegrees(A);
if ((ilat2 > ilat1) && (ilon2 > ilon1)) {
} else if ((ilat2 < ilat1) && (ilon2 < ilon1)) {
result = 180.0 - result;
} else if ((ilat2 < ilat1) && (ilon2 > ilon1)) {
result = 180.0 - result;
} else if ((ilat2 > ilat1) && (ilon2 < ilon1)) {
result += 360.0;
}
}
return result;
}
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