Measure and Pose coordinate of EKF

[cyberphantom]

Hi, I'm new working on ardrone project. I'm using this package to make use of EKF. I have a question on EKF inputs. When I monitoring the xy of measure and pose inputs. They are 0 all the time is that how it suppose to be or I have something wrong?
What about using the front camera instead of the bottom camera as it is the same concept to get a tag. I tried that and It works by configuring the video.channel to 0.
BTW I modify the condition in controller.js line 265 to (d.visionDetect && d.visionDetect.nbDetected >= 0) instead of (d.visionDetect && d.visionDetect.nbDetected > 0) to get it enter the loop.
Please if anyone working on this package I need your help,

Thanks,