目前能提供經緯度距離的算法有很多,以下方法是將地球看爲橢圓進行處理計算。具體算法過程不詳解(感興趣的可以網上搜索具體計算過程),這裏只列出代碼實現部分,代碼可以直接植入單片機中,進行計算。
注:由於地球是不規則的橢球體,並且實際地理位置還需考慮海拔情況,因此計算會存在一定誤差。
實際使用情況:本人採用了NEO-M8N的GPS&BD雙模定位模塊,測量有一定的距離誤差,不適於高精度場合,合適長距離估算。
#define PI 3.1415926
//度轉換成幅度值
double rad(double d)
{
return d * PI / 180.0;
}
/*******************************************************************************
* 函數名 : Get_GPSdistance
* 描述 : 計算經緯度距離
* 輸入 : 參數:第一點經度,緯度 ,第二點經度,緯度
* 返回 : 返回距離,單位M
* 注意 :
*******************************************************************************/
double Get_GPSdistance(double lon1, double lat1,double lon2, double lat2)
{
double EARTH_RADIUS = 6378137;
double x1 =0;
double y1 =0;
double z1=0;
double x2 =0;
double y2 =0;
double z2=0;
double d=0;
double theta=0;
double dist=0;
double radLat1 = rad(lat1);
double radLat2 = rad(lat2);
double radLon1 = rad(lon1);
double radLon2 = rad(lon2);
if (radLat1 < 0)
radLat1 = PI / 2 + abs(radLat1);// south
if (radLat1 > 0)
radLat1 = PI / 2 - abs(radLat1);// north
if (radLon1 < 0)
radLon1 = PI * 2 - abs(radLon1);// west
if (radLat2 < 0)
radLat2 = PI / 2 + abs(radLat2);// south
if (radLat2 > 0)
radLat2 = PI / 2 - abs(radLat2);// north
if (radLon2 < 0)
radLon2 = PI * 2 - abs(radLon2);// west
x1 = EARTH_RADIUS * cos(radLon1) * sin(radLat1);
y1 = EARTH_RADIUS * sin(radLon1) * sin(radLat1);
z1 = EARTH_RADIUS * cos(radLat1);
x2 = EARTH_RADIUS * cos(radLon2) * sin(radLat2);
y2 = EARTH_RADIUS * sin(radLon2) * sin(radLat2);
z2 = EARTH_RADIUS * cos(radLat2);
d = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)+ (z1 - z2) * (z1 - z2));
//餘弦定理求夾角
theta = acos((EARTH_RADIUS * EARTH_RADIUS + EARTH_RADIUS * EARTH_RADIUS - d * d) / (2 * EARTH_RADIUS * EARTH_RADIUS));
dist = theta * EARTH_RADIUS;
return dist/100.0; //比實際算法小100倍數 (M)
}