depthimage_to_laserscan : nothing published on /scan topic

edit

Hey,

I am trying to depthimage_to_laserscan package. i would attach an image of rqt_graph but the site wouldnt allow me to. Basically, I have the depthimage_to_laserscan node subscribed to camera_info and also the depth image topics. I also have a listener subscribed to the "/scan" topic

I have written a launch file to map the right topics correspondingly, but nothing is being published on /scan topic. could someone help me fix this?

thanks

this is the launch file i used:

<launch>

<node pkg="depthimage_to_laserscan" type="depthimage_to_laserscan" name="depthimage_to_laserscan">


  <remap from="image" to="/guidance/depth_image"/>
<remap from="camera_info" to="/guidance/camera_info"/>
</node>

</launch>

EDIT:

when I run

rosrun depthimage_to_laserscan depthimage_to_laserscan image:=/guidance/depth_image

I get the following warning

[ WARN] [1470083789.716155946]: [image_transport] Topics '/guidance/depth_image' and '/guidance/camera_info' do not appear to be synchronized. In the last 10s:
    Image messages received:      100
    CameraInfo messages received: 100
    Synchronized pairs:           0

Any thoughts on how to make them synchronized is much appreciated.