Normal of pointcloud2

edit

All the point cloud storage and manipulation in ROS is actually done using the Point Cloud Library, so this is what you'll use to calculate the normals of your point cloud.

There's a good page here which describes some of the theory of normal estimation from point clouds, as well as a worked example using the point cloud library.

http://pointclouds.org/documentation/tutorials/normal_estimation.php

This should get you moving in the right direction.