I have found a Very Interesting, recently published (Spring 2013), Article from Cornell University Entitled "Autonomous Quadcopter Docking System"
The really interisting thing about this is that it utilises a Video Camera to provide data to assist in the control of the quadcopter automatically using the live video feed.
It outlines Automatic detection and landing procedures for a Quadcopter using Ardupilot.
The system is designed so that the quadcopter can correctly determine the location of a target ground station and then land when above the target
There is also Python Script included in the article to implement the above procedure.
ARTICLE is at - http://people.ece.cornell.edu/land/courses/eceprojectsland/STUDENTPROJ/2012to2013/ssm92/ssm92_report_201305171020.pdf
There is also another Article - "Control, navigation and collision avoidance for an unmanned aerial vehicle"
on similar topic at - http://www.sciencedirect.com/science/article/pii/S092442471200698X
The reason for this Posting is to Promote COLLISION AVOIDANCE as a Urgently needed item in the next version of Code Release.
Replies
https://www.youtube.com/watch?v=qrbVVJJzy_Q
Very similar concept, figured I'd post the video here for any crossreferencing.