Input: the candidate detector set
Step . Sort CD in a descending order by the detector radius;
Step . Make sure that centers of detectors in the back of the sequence do not fall into the covered area of front detectors.
  That is to say, , where is the radius of detector , and is the size of ;
Step . Add candidate detectors into , and ensure that they do not entirely cover any detector in . That is to say,
     or and , where and are the radiuses
  of and respectively, and and are the sizes of and respectively.
Algorithm 6: The filtering process of candidate detectors.