Hybrid A*-Based Valley Path Planning Algorithm for Aircraft
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsSummary
The paper proposes a path planning algorithm based on 3D hybrid A* algorithm. The goal is to find a path based on aircraft dynamics and terrain (represented by DEMs) through a valley. The algorithm is tested in 3 environments. It is compared to 3 alternative algorithms (Dijkstra, APF, TRRT) with 4 objectives (average elevation, path length, valley points deviation, and time cost).
Comments
Chapter 1: Introduction
The introduction is well-written and structured. It also lists various alternative algorithms and discusses advantages and limitations.
Chapter 2
No comments
Chapter 3
No comments
Chapter 4
No comments
Chapter 5
The figures visualize very well the problem and its solution. The comparison of the proposed and reference algorithms is also well presented. However, I prefer the best value per column highlighted/bold in the tables instead of the last line. For example, table 1, average elevation of proposed algorithm bold; Path length of APF bold; Valley points deviation and time of proposed algorithm bold.
Additionally, a very brief description of the three reference algorithms would help the reader to understand the comparison. In particular, the differences between the proposed algorithm and the references. Then, the discussion also could go a little bit more into detail. Dijkstra, which is basically A* without a heuristic, finds shorter paths than the proposed algorithm in most cases. Why is that?
Chapter 6
Line 378 “We” should be “we” (small w)
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsDrawbacks of the manuscript are as follows.
1. Please, comment briefly basicmain distinctions between the proposed method and 3 known algorithms used for tests (fference Dijkstra, APF and TRRT). What has provided the obtained gain ?
2. What computer platform was used for testing?
3. Dynamic model part in sec.3.1. looks to be too separated from the following further material. Some additional commentary is desirable, disclosing the idea of interaction of output parameters of the model given in sec. 3.1 with the further proposed valley path procession method.
4. In sec. 4.1 it is necessary to explain basic procedures to process open and closed lists (Sopen and Sclosed ).
5. Explain, what is the valley cost in Algorithm 2.
6. In sec. 4.3 the phrase in rows 270-272 concerning the actual cost is not clear enough. Further, it is preferable to comment possible methods to obtain components of the heuristic cost.
7. Disclose, why the path G has -1 parameter in row 174.
8. Fig. 1 contains 3 excessive projections of an aircraft, which are not really used in the text, but the angles were not shown.
9. Check please, exp. (9-10), as before them qv was defined as a vector value.
10. Misprint “extened” is to be corrected in Algorithm 1.
Comments on the Quality of English Language
Some language corrections are possible.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsAll concerns I raised were adequately considered.
Thank you for your work.
