用map快速查找

有需要快速查找的数时可以用map

 std::map<std::string, cv::Point3d> all_gps_data;
 std::map<std::string, cv::Point3d>::iterator iter_ =  all_gps_data.find(image_name);
    if(iter_ != all_gps_data.end())
      {
        current_gps=iter_->second;
      }