source /opt/ros/noetic/setup.bash
    
    # catkin_make

    source ~/catkin_ws/devel/setup.bash

    catkin_create_pkg test1 roscpp

    # cmake options
    -DPYTHON_EXECUTABLE=/usr/bin/python3 -DCATKIN_DEVEL_PREFIX:PATH=/home/jianping/catkin_ws/devel

    # build directory
    /home/jianping/catkin_ws/build

    #include <ros/ros.h>
    #include <tf/transform_broadcaster.h>
    #include <nav_msgs/Odometry.h>
    
    int main(int argc, char** argv){
        ros::init(argc, argv, "odometry");
    
        ros::NodeHandle n;
        ros::Publisher odom_pub = n.advertise<nav_msgs::Odometry>("odom", 50);
        tf::TransformBroadcaster odom_broadcaster;
    
        double x = 0.0;
        double y = 0.0;
        double th = 0.0;
    
        double vx = 0.1;
        double vy = -0.1;
        double vth = 0.1;
    
        ros::Time current_time, last_time;
        current_time = ros::Time::now();
        last_time = ros::Time::now();
    
        ros::Rate r(1.0);
        while(n.ok()){
    
            ros::spinOnce();               // check for incoming messages
            current_time = ros::Time::now();
    
            //compute odometry in a typical way given the velocities of the robot
            double dt = (current_time - last_time).toSec();
            double delta_x = (vx * cos(th) - vy * sin(th)) * dt;
            double delta_y = (vx * sin(th) + vy * cos(th)) * dt;
            double delta_th = vth * dt;
    
            x += delta_x;
            y += delta_y;
            th += delta_th;
    
            //since all odometry is 6DOF we'll need a quaternion created from yaw
            geometry_msgs::Quaternion odom_quat = tf::createQuaternionMsgFromYaw(th);
    
            //first, we'll publish the transform over tf
            geometry_msgs::TransformStamped odom_trans;
            odom_trans.header.stamp = current_time;
            odom_trans.header.frame_id = "odom";
            odom_trans.child_frame_id = "base_link";
    
            odom_trans.transform.translation.x = x;
            odom_trans.transform.translation.y = y;
            odom_trans.transform.translation.z = 0.0;
            odom_trans.transform.rotation = odom_quat;
    
            //send the transform
            odom_broadcaster.sendTransform(odom_trans);
    
            //next, we'll publish the odometry message over ROS
            nav_msgs::Odometry odom;
            odom.header.stamp = current_time;
            odom.header.frame_id = "odom";
    
            //set the position
            odom.pose.pose.position.x = x;
            odom.pose.pose.position.y = y;
            odom.pose.pose.position.z = 0.0;
            odom.pose.pose.orientation = odom_quat;
    
            //set the velocity
            odom.child_frame_id = "base_link";
            odom.twist.twist.linear.x = vx;
            odom.twist.twist.linear.y = vy;
            odom.twist.twist.angular.z = vth;
    
            //publish the message
            odom_pub.publish(odom);
    
            last_time = current_time;
            r.sleep();
        }
    }