Research on Three-Dimensional Electronic Navigation Chart Hybrid Spatial Index Structure Based on Quadtree and R-Tree

Round 1

Reviewer 1 Report

Dear colleagues, 

thank you for your contribution on "three-dimensional Electronic Navigation Chart hybrid spatial index structure based on Quad-tree and R-tree". The paper is easy to read, the research method is clear and the results and argumentation are supported by the observations of the query time. 

I have nothing to add. Thank you for this insightful paper, which was interesting to read. 

Author Response

Thank you for the detailed review of our manuscript and your valuable input. 

Reviewer 2 Report

The paper has a strong focus on maritime application and its necessary navigation charts. During the reading, the reviewer felt not have enough domain-specific (maritime) knowledge and related terms (e.g., S-101 doesn’t say too much – I had to google to understand the context). This approach must be improved to have average GIS readers on board!

I don’t want to comment on language issues; the text was generally clear and understandable (once more, beyond the formerly mentioned lack of naval knowledge).

The paper seems to have over dimensioned amounts of very similar illustrations (Fig. 9-11, Fig. 13).

The details of the critics are the following:

• line 14: S-101 standard is a document with meaning for only naval-related people. As a general background GIS user, I do not have a sufficient understanding of the topic – I hope that the paper will explain it somewhat. It still fails, so I had to google for it.
• line 16: I don’t know and understand the difference between the minimum bounding box and the smallest minimum bounding box. If there is a difference, it is crucial to explain it. Otherwise, smallest and minimum are synonyms…
• line 68: same as line 14
• line 78 and next: quadtree is clearly 2D and octree 3D, maybe a more robust formulation helps in better understanding
• line 80: octree dynamic adjustment: as far as I have known, Lidar point cloud management software solve this challenge, they can manage arbitrary distributed spatial point clouds.
• line 125: starting a sentence with ‘and’ sounds strange; please rewrite it
• line 126-127: it is an unended (truncated) sentence. Please rewrite it!
• line 131-132, line 134: the listed items (e.g., Geo Features) mustn’t write in capitals
• line 131: Geo Feature seems jargon; what is geo stand for? Geometry? in the current scientific paper, clarity is essential! Please fix all occurrences!
• line 145: ground can be written in small letters
• Table 1: the presentation of the complete feature catalog seems unnecessary; maybe some relevant examples are enough to explain the problem. Furthermore, Fig. 3 is also a kind of list
• line 173: terms can be written in small letters
• line 217: “too many levels” I think if we generally speak about 3D objects, there is not much sense in mentioning levels. When talking about water depths, it is the same spatial problem. (I know that levels can be differentiated, but digital data management shall not limit to levels…)
• line 236: what is an “envelope of nodes”? Please explain in the text
• line 239: instead of using capitals: pointer
• line 241: again SMBB vs. MBB. A clarification is crucial!
• 4: OGR occurs several times: what does it mean?
• line 259: what is the difference between SMBB and envelope??
• line 265: threshold QK. what type of threshold is it, and how is it used in controlling the workflow? Is it just a parameter having an empirically determined value? What is it numerically? Maybe an example can be taken…
• line 362-364: I don’t understand this optimization fully. What was the goal exactly? What type of optimizer was used? How can an optimization derive SMBB from MBB (where my original question rises again!)?
• 9 and 10: they seem to be just a placeholder. Without essential explanation, these charts tell very few!
• line 416-422: I can’t recognize the described distant and close-up views) all map cut-offs are from different places, and the connecting figures are only top and perspective views. Please explain it more clearly, what the focus is, and how to understand the differences!
• Table 4: feature names seem only as abbreviations; maybe a full term in parenthesis can help in better understanding
• line 464: appendix isn’t in the text; this list can be skipped

I think that the paper can be fixed and after major revision, it can be accepted.

Author Response

Thank you for the detailed review of our manuscript and your valuable input. We have revised accordingly and in detail by addressing each of the questions and points raised. We subsequently hope that the content of this paper has more clarity after undergoing this intensive revision. All adjustments and improvements have been made on the revised paper according to your suggestions and comments. 

Author Response File: Author Response.docx

Reviewer 3 Report

The problem of spatial indexing is common for many LBS applications. In most cases, it is solved by using standard indices in the DB engine used in the system. However, when high performance is needed then optimizations in spatial indexing may solve the problem. The article presents implementation details of such a solution and discusses how to configure the structure of the index depending on data characteristics.

The paper is written clearly, and it is easy to understand the problem and the presented solution. The main issue with the article is that the results are presented not clearly enough which makes it difficult to understand the results.

Suggestions:

• Figure 2. I would rather expect a schema of experiments rather than an organizational structure of the article
• Figure 3. I don't understand what the colours of the elements represent.
• Line 268. "Three R-trees were constructed...", better: "R-trees were constructed...",
• Figure 6. Please explain the symbols in the figure.
• Table 3. No units, not all lines are clear even after reading a text before.
• Figures 9-12. Unreadable, low-quality rasters.
• Figure 13. Presented frames are not discussed in the text. What is the message the authors wanted to illustrate?

Author Response

Thank you for the detailed review of our manuscript and your valuable input. We have revised accordingly and in detail by addressing each of the questions and points raised. We subsequently hope that the content of this paper has more clarity after undergoing this intensive revision. All adjustments and improvements have been made on the revised paper according to your suggestions and comments. 

Author Response File: Author Response.docx