地理坐标系介绍
主流地理坐标系、投影坐标系和投影方法的区别和联系_ 一只博客-CSDN博客/qq_42276781/article/details/122597363关于坐标系的转换，可以参考如下两个开源项目gcoord和coordtransform
GitHub - hujiulong/gcoord: 地理坐标系转换工具/hujiulong/gcoordGitHub - wandergis/coordtransform: 提供了百度坐标（BD09）、国测局坐标（火星坐标，GCJ02）、和WGS84坐标系之间的转换/wandergis/coordtransform我将gcoord中的BD09和WGS84互转的代码改写成了C语言的形式，便于大家理解。
通过BD09和GCJ02的互转与GCJ02和WGS84的互转来实现BD09和WGS84的互转，即
1）BD09 => GCJ02 => WGS84
2）WGS84 => GCJ02 => BD09
下面的代码结合了我之前的两篇博客（核心思想均参考自Gcoord）
地理坐标系：GCJ02和BD09互转_ 一只博客-CSDN博客/qq_42276781/article/details/122596686地理坐标系：GCJ02和WGS84互转_ 一只博客-CSDN博客_wgs84坐标系/qq_42276781/article/details/121388429BD09和WGS84的互转代码
#include<stdio.h>#include<math.h>#include<stdlib.h>#define PI 3.1415926535897932384626double* BD09ToWGS84(double, double);double* WGS84ToBD09(double, double);double* BD09ToGCJ02(double, double);double* GCJ02ToBD09(double, double);double* GCJ02ToWGS84(double, double);double* WGS84ToGCJ02(double, double);int main(){double lon = 116.403988;double lat = 39.914266;double *p = WGS84ToBD09(lon, lat);printf("%.10f, %.10f", p[0], p[1]);}// (BD09 <=> WGS84) base on (BD09 <=> GCJ02) and (WGS84 <=> GCJ02)double* BD09ToWGS84(double lon_BD, double lat_BD){double *GCJ = BD09ToGCJ02(lon_BD, lat_BD);return GCJ02ToWGS84(GCJ[0], GCJ[1]);} double* WGS84ToBD09(double lon_WGS, double lat_WGS){double *GCJ = WGS84ToGCJ02(lon_WGS, lat_WGS);return GCJ02ToBD09(GCJ[0], GCJ[1]);} // BD09 <=> GCJ02double baiduFactor = (PI * 3000.0) / 180.0;double* BD09ToGCJ02(double lon_BD, double lat_BD){double *GCJ = (double *)malloc(2*sizeof(double));double x = lon_BD - 0.0065;double y = lat_BD - 0.006;double z = sqrt(x * x + y * y) - 0.00002 * sin(y * baiduFactor);double theta = atan2(y, x) - 0.000003 * cos(x * baiduFactor);GCJ[0] = z * cos(theta);GCJ[1] = z * sin(theta);return GCJ;}double* GCJ02ToBD09(double lon_GCJ, double lat_GCJ){double *BD = (double *)malloc(2*sizeof(double));double z = sqrt(lon_GCJ * lon_GCJ + lat_GCJ * lat_GCJ) + 0.00002 * sin(lat_GCJ * baiduFactor);double theta = atan2(lat_GCJ, lon_GCJ) + 0.000003 * cos(lon_GCJ * baiduFactor);BD[0] = z * cos(theta) + 0.0065;BD[1] = z * sin(theta) + 0.006;return BD;} // WGS84 <=> GCJ02double a = 6378245;double ee = 0.006693421622965823;// roughly check whether coordinates are in China.int isInChinaBbox(double lon, double lat){return lon >= 72.004 && lon <= 137.8347 && lat >= 0.8293 && lat <= 55.8271;}double transformLat(double x, double y){double ret = -100.0 + 2.0 * x + 3.0 * y + 0.2 * y * y + 0.1 * x * y + 0.2 * sqrt(fabs(x));ret += ((20.0 * sin(6.0 * x * PI) + 20.0 * sin(2.0 * x * PI)) * 2.0) / 3.0;ret += ((20.0 * sin(y * PI) + 40.0 * sin((y / 3.0) * PI)) * 2.0) / 3.0;ret += ((160.0 * sin((y / 12.0) * PI) + 320.0 * sin((y * PI) / 30.0)) * 2.0) / 3.0;return ret;}double transformLon(double x, double y){double ret = 300.0 + x + 2.0 * y + 0.1 * x * x + 0.1 * x * y + 0.1 * sqrt(fabs(x));ret += ((20.0 * sin(6.0 * x * PI) + 20.0 * sin(2.0 * x * PI)) * 2.0) / 3.0;ret += ((20.0 * sin(x * PI) + 40.0 * sin((x / 3.0) * PI)) * 2.0) / 3.0;ret += ((150.0 * sin((x / 12.0) * PI) + 300.0 * sin((x / 30.0) * PI)) * 2.0) / 3.0;return ret;}double* delta(double lon, double lat){double *d = (double *)malloc(2*sizeof(double));double dLon = transformLon(lon - 105.0, lat - 35.0);double dLat = transformLat(lon - 105.0, lat - 35.0);double radLat = (lat / 180.0) * PI;double magic = sin(radLat);magic = 1.0 - ee * magic * magic;double sqrtMagic = sqrt(magic);d[0] = (dLon * 180.0) / (a / sqrtMagic * cos(radLat) * PI);d[1] = (dLat * 180.0) / ((a * (1.0 - ee)) / (magic * sqrtMagic) * PI);return d;}double* WGS84ToGCJ02(double lon_WGS, double lat_WGS){double *GCJ = (double *)malloc(2*sizeof(double));if (!isInChinaBbox(lon_WGS, lat_WGS)){GCJ[0] = lon_WGS;GCJ[1] = lat_WGS;return GCJ;} double *d = delta(lon_WGS, lat_WGS);GCJ[0] = lon_WGS + d[0];GCJ[1] = lat_WGS + d[1];return GCJ;}double* GCJ02ToWGS84(double lon_GCJ, double lat_GCJ) {double *WGS = (double *)malloc(2*sizeof(double));if (!isInChinaBbox(lon_GCJ, lat_GCJ)){WGS[0] = lon_GCJ;WGS[1] = lat_GCJ;return WGS;} WGS[0] = lon_GCJ; WGS[1] = lat_GCJ;double *temp = WGS84ToGCJ02(WGS[0], WGS[1]);double dx = temp[0] - lon_GCJ;double dy = temp[1] - lat_GCJ;while (fabs(dx) > 1e-6 || fabs(dy) > 1e-6) {WGS[0] -= dx;WGS[1] -= dy;temp = WGS84ToGCJ02(WGS[0], WGS[1]);dx = temp[0] - lon_GCJ;dy = temp[1] - lat_GCJ;}return WGS;}
