Research on GNSS/IMU/Visual Fusion Positioning Based on Adaptive Filtering
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsIn this manuscript, the authors propose a technique on the GNSS, IMU, and Visual odometry fusion to mitigate the positioning accuracy in GNSS-denied areas. The proposed idea is validated in a real scenario using a smartphone. The manuscript discusses an interesting topic and the real-world measurement campaign is an added value to the manuscript. However, I cannot recommend the publication in this form. Please find below some comments which may help the authors to improve the manuscript quality.
- Introduction: The introduction should be concluded with a clear statement of the contributions offered by the manuscript, along with a description of the paper's organization.
- Introduction: I think authors should also include in their introduction GNSS applications other than the classical MEO Beidou/GPS. For instance, you can discuss LEO coarse positioning systems which are based on the Angle-of-Arrival estimation of signals of opportunity as a possible option to aid MEO GNSS systems in GNSS-denied areas.
- Please improve the formulas and page formatting for pages 3 and 4.
- Section 4.1: when you discuss the hardware platform for the experimental campaign, you should put some references to the datasheet or product pages.
- Section 4.1: Usually smartphones are equipped with AGPS sensors, therefore the GNSS positioning is already aided with other sources like Wi-Fi or LTE features. Did you unbias your measurements from these elements?
- Section 4.2: Does the introduced technique have an impact on the time to first estimation concerning the simple GNSS positioning? Are you able to qualitatively give an insight on this aspect, or just empirically give an idea of this aspect?
- Figure 4: Please increase the figure font
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for Authors- More details about the influence of the parameters of the adaptive filter and the numerical complexity could be beneficial for the paper.
- The typesetting of the inline equations should be improved.
- The authors could mention the simplified Kalman filter, the hybrid simplified Kalman filter, and their application for integrated navigation or adaptive feedback cancellation.
- There are inconsistencies in the reference section that should be corrected (e.g., the names of the authors are written in various forms - . Sun, Yan G, FAN Lei, etc).
- To promote reproducible research, I recommend that the authors, if feasible, share the relevant source codes on platforms like GitHub, their research group's website, or a similar repository. This initiative could significantly benefit the academic community.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsA brief summary: In the publication, the authors present a method for combining different sensors to improve positioning accuracy. The proposed approach is quite new and interesting.
General concept comments: The introduction presents a general overview of the used method and research area. However, this overview needs to be expanded and supplemented (see Specific comment 1). There is no methodology in its classical sense, but the methodology is presented in two separate sections, but it needs some clarification (see Specific comment 2). Experimental analysis and results are described in detail in Chapter 4, but some aspects need clarification (see Specific comments 3-5). There is no discussion in the publication (see Specific comment 6). The conclusions quite succinctly summarize the results of the research. The list of references is relevant and quite new, but too short (see Specific comment 7).
Specific comments
1. The introduction should provide a critical analysis of the known methods and justify the relevance of the new research. There is no critical analysis in the introduction. Since the topic of the study is very popular nowadays, it is recommended to review more literature sources in the introduction, which are quite numerous.
2. The flowchart provided by the authors (Figure 1) is necessary, but I believe that it should be located and generally described in a new section - ‘2. Methodology’ and the existing sections 2 and 3 should be integrated into this methodology as 2.1 and 2.2 respectively.
3. The authors mention different software, but do not specify the type of license. And if the license is not open access, I think it is necessary to indicate the number of this license.
4. Since there is an accumulation of errors along the way in the methods used, it is necessary to clearly indicate the beginning and end of the tracks in Figures 2 and 4.
5. The authors mention many different sensors, but do not provide general information about them (e.g. country of manufacture, manufacturer, possibly a link to the website, etc.).
6. The discussion should be included in the publication, as it is one of the most important parts of the publication. Discussions must contain a critical analysis of the obtained results in comparison with other studies.
7. The analysis of only 12 literature sources in the publication is unacceptable. I recommend expanding this list by two or even three times. This can be easily done by addressing Specific comments 1 and 6.
8. A final criticism, which applies to the entire publication, is that the authors use a large number of abbreviations, but do not provide the decoding of these abbreviations when they are first mentioned in the text. It is recommended to correct this in the text, or add a catalog of used abbreviations in the application.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors revised the manuscript according to my comments. Below I put some comments that may help the authors to improve the manuscript quality further.
- A description of the paper's organization at the end of the Introduction is still missing. Also, I suggest putting your contribution in a more systematic way, for instance using a bullet point list.
- The authors included in the Introduction some GNSS applications other than the classical MEO. To complete your literature survey, you can include also systems based on signals of opportunity, e.g. LEO coarse positioning systems which are based on the Angle-of-Arrival estimation of signals of opportunity.
- I suggest putting some of the concepts in the answer to Comment #6 in the paper.
- The authors should pay attention to correctly formatting the references. When web pages are referenced, please state the title of the web page and the date on which the source was accessed. Moreover, references 28-29 should be better formatted.
Author Response
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Author Response File: Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors have sufficiently addressed my comments.
Author Response
Thank you for all your comments on this manuscript.
