We are using Astra in this robot to replicate the function of an expensive laser range scanner. The depth image is processed and converted to the data equivalent of a laser scanner using ROS's depthimage_to_laserscan package (see http://wiki.ros.org/depthimage_to_laserscan for more information).
You can either install this package from the source code or use the Ubuntu package manager. Here is the command to install this package from the Ubuntu package manager
$ sudo apt-get install ros-<version>-depthimage-to-laserscan
The main function of this package is to slice a section of the depth image and convert it to an equivalent laser scan data type. The ROS sensor_msgs/LaserScan message type is used for publishing the laser scan data. This depthimage_to_laserscan package will perform this conversion and fake the laser...