A New Skeleton Feature Extraction Method for Terrain Model Using Profile Recognition and Morphological Simplification

Algorithm 6

Repeated pruning of MPPA.

Input: The current segments set seg_res, ring

   segments set seg_br, and out branch sign

   array 𝐴_𝑜.

Output: The result segments set seg_res with the

   final skeleton features.

1. Let 𝐴_𝑏 be branch points array produced in Section

 4.1 and let loop = 1 as loop times.

2. Call Algorithm 5 to update the out-branching set

 𝐴_𝑜 of the current segments set seg_res.

3. Let length_criterion be criterion of branch length.

4. Search the unchecked directions of adjacent points

 of 𝑝∈𝐴_𝑏, until reach the end points of this

 branch.

5. For each branch 𝑒_𝑏 at the beginning of 𝑝:

 5.1 Let length_criterion=length_criterion+loop;

 5.2 Calculate the length 𝑛 of 𝑒_𝑏;

 5.3 If 𝑛<length_criterion, then eliminate 𝑝 and

   the branch 𝑒_𝑏;

 5.4 Check direction coefficient of 𝑝, if there is the

   direction that has not be traversed, then go to

   step 4;

 5.5 loop=loop+1.

6. Retrieval the stable ring according to ring segments

 set seg_br.

7. Retrieval the out branch according to

 out-branching sign array 𝐴_𝑜.

8. Algorithm end.