ORBSLAM输出的轨迹与数据集真实轨迹进行空间轨迹对齐并输出txt文件C++代码

对轨迹进行空间对齐，需要先确定两个轨迹的参考系。假设数据集真实轨迹为基准参考系，我们需要将ORBSLAM输出的轨迹变换到基准参考系下。

以下是一份示例代码，实现了将ORBSLAM输出的轨迹与数据集真实轨迹进行空间对齐并输出txt文件：

#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <Eigen/Core>
#include <Eigen/Geometry>

using namespace std;
using namespace Eigen;

// 定义一些常量
const string dataset_path = "/path/to/dataset";  // 数据集路径
const string orbslam_path = "/path/to/orbslam/results.txt";  // ORBSLAM输出的轨迹文件路径
const string output_path = "/path/to/output/results.txt";  // 对齐后输出的轨迹文件路径

// 读取真实轨迹文件
void read_groundtruth(const string& filename, vector<Isometry3d>& poses)
{
    ifstream fin(filename);
    if (!fin)
    {
        cerr << "无法打开真实轨迹文件：" << filename << endl;
        return;
    }

    while (!fin.eof())
    {
        double timestamp, tx, ty, tz, qx, qy, qz, qw;
        fin >> timestamp >> tx >> ty >> tz >> qx >> qy >> qz >> qw;

        Quaterniond q(qw, qx, qy, qz);
        Isometry3d pose = Isometry3d::Identity();
        pose.translate(Vector3d(tx, ty, tz));
        pose.rotate(q);

        poses.push_back(pose);
    }

    fin.close();
}

// 读取ORBSLAM输出的轨迹文件
void read_orbslam(const string& filename, vector<Isometry3d>& poses)
{
    ifstream fin(filename);
    if (!fin)
    {
        cerr << "无法打开ORBSLAM输出的轨迹文件：" << filename << endl;
        return;
    }

    while (!fin.eof())
    {
        double timestamp, tx, ty, tz, qx, qy, qz, qw;
        fin >> timestamp >> tx >> ty >> tz >> qx >> qy >> qz >> qw;

        Quaterniond q(qw, qx, qy, qz);
        Isometry3d pose = Isometry3d::Identity();
        pose.translate(Vector3d(tx, ty, tz));
        pose.rotate(q);

        poses.push_back(pose);
    }

    fin.close();
}

int main()
{
    // 读取真实轨迹和ORBSLAM输出的轨迹
    vector<Isometry3d> groundtruth, orbslam;
    read_groundtruth(dataset_path + "/groundtruth.txt", groundtruth);
    read_orbslam(orbslam_path, orbslam);

    // 对齐轨迹
    Isometry3d T_orbslam_to_groundtruth = groundtruth[0].inverse() * orbslam[0];
    for (auto& pose : orbslam)
    {
        pose = T_orbslam_to_groundtruth * pose;
    }

    // 输出对齐后的轨迹
    ofstream fout(output_path);
    if (!fout)
    {
        cerr << "无法打开输出文件：" << output_path << endl;
        return -1;
    }

    for (size_t i = 0; i < groundtruth.size(); ++i)
    {
        Isometry3d pose = groundtruth[i].inverse() * orbslam[i];
        Quaterniond q(pose.rotation());
        Vector3d t(pose.translation());

        fout << fixed << setprecision(6) << groundtruth[i].matrix()(0, 3) << " ";
        fout << fixed << setprecision(6) << groundtruth[i].matrix()(1, 3) << " ";
        fout << fixed << setprecision(6) << groundtruth[i].matrix()(2, 3) << " ";
        fout << fixed << setprecision(6) << q.x() << " ";
        fout << fixed << setprecision(6) << q.y() << " ";
        fout << fixed << setprecision(6) << q.z() << " ";
        fout << fixed << setprecision(6) << q.w() << endl;
    }

    fout.close();

    cout << "轨迹已对齐并输出到文件：" << output_path << endl;

    return 0;
}

需要注意的是，上述代码中的Isometry3d是Eigen库中提供的一个类，表示欧几里德变换（旋转+平移）。对于一个姿态矩阵（即旋转矩阵和平移向量组成的4x4矩阵），可以使用Isometry3d类来进行读取和变换。在输出对齐后的轨迹时，需要将旋转矩阵和平移向量分别提取出来，并将旋转矩阵转换为四元数表示。