给车的经纬度和高度，再给一个目标点的经纬度，知道目标点在相对车的什么位置用C++语言实现

这里提供一个简单的 C++ 函数示例，可以通过车的经纬度和高度，以及目标点的经纬度，计算出目标点在相对车的位置。

#include <iostream>
#include <cmath>

using namespace std;

#define EARTH_RADIUS 6371.0 // 地球半径，单位为 km

struct Point {
    double x, y, z;
};

// 计算两点之间的距离，单位为 km
double distance(double lat1, double lon1, double alt1, double lat2, double lon2, double alt2) {
    double dLat = (lat2 - lat1) * M_PI / 180.0;
    double dLon = (lon2 - lon1) * M_PI / 180.0;
    double a = sin(dLat / 2) * sin(dLat / 2) + cos(lat1 * M_PI / 180.0) * cos(lat2 * M_PI / 180.0) * sin(dLon / 2) * sin(dLon / 2);
    double c = 2 * atan2(sqrt(a), sqrt(1 - a));
    double d = EARTH_RADIUS * c;
    return sqrt(d * d + (alt2 - alt1) * (alt2 - alt1));
}

// 计算两点之间的方位角，单位为度
double bearing(double lat1, double lon1, double lat2, double lon2) {
    double dLon = (lon2 - lon1) * M_PI / 180.0;
    double y = sin(dLon) * cos(lat2 * M_PI / 180.0);
    double x = cos(lat1 * M_PI / 180.0) * sin(lat2 * M_PI / 180.0) - sin(lat1 * M_PI / 180.0) * cos(lat2 * M_PI / 180.0) * cos(dLon);
    double bearing = atan2(y, x) * 180.0 / M_PI;
    return bearing;
}

// 计算目标点在相对车的位置和角度
void relativePosition(double carLat, double carLon, double carAlt, double targetLat, double targetLon) {
    double dist = distance(carLat, carLon, carAlt, targetLat, targetLon, 0.0);
    double bearing = bearing(carLat, carLon, targetLat, targetLon);
    double angle = 0.0;
    if (bearing >= -45.0 && bearing < 45.0) {
        angle = bearing;
        cout << "目标点在相对车的前方，距离为 " << dist << " km，方位角为 " << angle << " 度" << endl;
    } else if (bearing >= 45.0 && bearing < 135.0) {
        angle = bearing - 90.0;
        cout << "目标点在相对车的左侧，距离为 " << dist << " km，方位角为 " << angle << " 度" << endl;
    } else if (bearing >= -135.0 && bearing < -45.0) {
        angle = bearing + 90.0;
        cout << "目标点在相对车的右侧，距离为 " << dist << " km，方位角为 " << angle << " 度" << endl;
    } else {
        angle = bearing + 180.0;
        cout << "目标点在相对车的后方，距离为 " << dist << " km，方位角为 " << angle << " 度" << endl;
    }
}

int main() {
    // 以北京市中心点和故宫两点为例
    double carLat = 39.9042;
    double carLon = 116.4074;
    double carAlt = 50.0;
    double targetLat = 39.9163;
    double targetLon = 116.3972;
    relativePosition(carLat, carLon, carAlt, targetLat, targetLon);
    return 0;
}

这个示例中，我们通过 `distance()` 函数计算两点之间的距离，通过 `bearing()` 函数计算两点之间的方位角，然后根据方位角将目标点在相对车的位置进行判断并输出。你可以根据实际情况进行调整。