Unable to push_back float64 custom msg in std::vector<std_msgs::Float64>

edit

I have a custom message as follows:

sensor_msgs/PointCloud2 velodynepoints 
float64[3] velodynenormal

and a subscriber nodelet with the following callback function

void class_name::func_name(const pkg_name::msg_file_name::ConstPtr &data) 
{
for (int i = 0; i < 3; i++) {
velodyne_n.push_back(data->velodynenormal[i]);
}
}

where velodyne_n is std::vector< std_msgs::Float64 > velodyne_n; However, I get the following error:

no matching function for call to ‘std::vector<std_msgs::Float64_<std::allocator<void> > >::push_back(const double&)’
 velodyne_n.push_back(data->velodynenormal[i]);
                                             ^

but if I define velodyne_n as std::vector<float> velodyne_n, I get no errors. Can someone help in pointing out where I might be going wrong? Thanks!