How can i write a publisher for /GPSFix message from Velodyne Lidar?

edit

I found. This is the code.

#include "ros/ros.h"
#include <gps_common/GPSFix.h>

void GPSCallback(const gps_common::GPSFix::ConstPtr& msg)
{
std::cout<<"Latitude: "<<msg->latitude<<"\t"<<"Longitude: "<<msg->longitude<<"\n";
}

int main(int argc, char **argv)
{

  ros::init(argc, argv, "listener");


  ros::NodeHandle n;


  ros::Subscriber sub = n.subscribe("/GPSFix", 1000, GPSCallback);


  ros::spin();

  return 0;
}