An Improved Innovation Robust Outliers Detection Method for Airborne Array Position and Orientation Measurement System
Round 1
Reviewer 1 Report
An adaptive outlier tolerant combined estimation method is proposed to estimate the position signals of the array POS system in the article. The semi-physical experiments are conducted, and the results verified that this estimation method could improve the estimation accuracy on the position, the velocity and the attitude angle. However, some minor errors shoudl be revised in the further version.
1, the mathmatical writting including the formulas and the symbols should be uniform
2, the flowchart about the estimation method in the experiment should be added
3, the descripts about the experimental results should be improved, and the data using different methods at different processes should be briefly introduced.
Author Response
Please see the attachment
Author Response File: 
Author Response.docx
Reviewer 2 Report
A brief summary
The inertial devices and measurement systems of array POS are vulnerable to strong interference environment, which leads to the decline or even divergence of the accuracy of their combined results. An adaptive estimation method for detection of abnormal values of inertial devices and measurement information is proposed.
General concept comments
An adaptive outlier tolerant combined estimation method for array POS is proposed. Semi-physical simulation in conjunction with data obtained during flight test is used to test the effectiveness of the proposed method. Outliers are added into the obtained data array and the simulation is performed without outlier detection and with outlier detection by the proposed method. There is no reasoning behind the abnormal value parameters choice. Random outlier parameters (mean value and variance) are chosen, moreover, they are the same for the height, heading, vertical velocity and for accelerometer, gyroscope measurements. Justification of the parameters choice is needed, does it correspond to the conditions of the experiments and the equipment used? Besides, stable flight section is used for the semi-physical simulation. But it would be more correct to test the proposed method on the sections with maneuvering to see how the proposed algorithm copes with the changes in measurements (caused by the movement or wing vibration) against which it is necessary to detect the abnormal measurement. Outlier detection in semi-constant measurements could be done with simpler algorithms.
There is no comparison of the proposed method with the methods presented in overview. It is impossible to judge the advantages of the proposed method. Data after the outlier removal is compared with the data before outlier removal, but it would be much more interesting to compare various methods of outlier detection and removal.
Specific comments
1. Line 41. In the text there are no references to (1-8 ) from the reference list.
2. Formula (4). The order of parameters is mixed up. In formula (4) accelerometer parameters go first, and the gyroscope parameters are second, but in formulas (2) and (3) gyroscope parameters are first, and accelerometers parameters are second.
3. Formula (8). Matrix element HG diag{RM,RN,cosL,1} is written incorrectly. It is dimensioned 4Ñ…4, but should be 3Ñ…3. Besides, RM,RN,L are not explained.
4. Formulas (8) and (13). In formula (13) elements of attitude matrix С are used, but in formula (8) to denote the same values the variables introduced in formulas (9), (10) are used. It is necessary to use same designations.
5. Formula (29). "i" symbol is used to indicate two different things: both as an angular velocity and acceleration index and as time indicator.
6. Formula (29). There is no description of coefficient 'a' calculation algorithm.
7. Line 219. It is not specified over which interval the value of e(k) is determined.
8. Formula (32). Indexes in the second expression are incorrect.
9. Line 221. 'К' is used instead of 'k'.
10. Chapter 4. There is confusion in the left node naming: in lines 247, 250, 264, 278, 282, 325, 331, figures 5,6,8, Tables 3, 4 it is called «left node», in lines 276, 281, 324, 329 «life node», and in figures 7, 9 «lift node».
11. Table 2. Matrix 'Q' is dimensioned 9Ñ…9, but in formula (4) 'Q' has dimensions 6Ñ…6.
12. Figure 8. In the figure caption (b) gyroscopes are stated instead of accelerometers.
13. Line 365-367. Sentence repeats 2 times.
Author Response
Please see the attachment
Author Response File: Author Response.docx
Reviewer 3 Report
in attachment
Comments for author File: 
Comments.pdf
Author Response
Please see the attachment
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
The authors have done a good job, most of the comments have been eliminated.
The following remarks remain:
1. Equation 8 Matrix element HG diag{RM,RN,cosL,1} corrected with an mistake. Should be diag{RM,RN∙cosL,1}.
2. Equation 29 The summation must be done by "j".
3. There is confusion in the left node naming as before: «left node» and «lift node» are used.
Author Response
Please see the attachment
Author Response File: Author Response.docx
Reviewer 3 Report
GENERAL COMMENTS:
The authors have done considerable work to correct and improve the text of the article. The work has become better for the perception of an ordinary reader, as well as for understanding the conditions for conducting experiments and interpreting the results obtained. However, by mistake, I did not include some of the questions to the authors in the text of the first review. I'll list them here. And some suggestions for improvement, which are given below.
MAJOR COMMENTS:
1. I would like to draw your attention to the authors' use of the term "Array POS", especially in the title of the article. This term is not a generic or technical term. The average reader, seeing this abbreviation in the title of the article, is likely to think that we are talking about methods of positioning in an array of data for the Python programming language, for example, rather than aircraft-based navigation hardware. It is desirable to mention a navigation device or airborne systems in the title and then define and use the term "Array POS" in the text of the article.
2. The comments given by the authors in the text of the review are very valuable and useful not only as a response to the reviewer, but also for ordinary readers to understand the meaning of the experiments conducted. And in one way or another I would like to see the text of these responses with the article itself. Like these:
“But the consequence of all types of deliberate jamming is that there are outliers in measurement data or in inertial devices data. Referring to a large number of flight test and vehicle test data, we find that outliers mainly has two forms: isolated type and continuous type. Therefore, in this paper, discrete and continuous noises are superimposed on normal measurement data to simulate measurement data under strong interference environment. Due to length limitations, there is really no description of various types of deliberate jamming, which not mean that the proposed mothed will not work in these conditions”;
or
“However, the implementation of a flight experiment requires large amount of manpower, material resources and financial resources. Simulation experiments based on real flight data are often used to verify the effectiveness of the method in the navigation system, which is called Semi-physical simulation experiment or physical mathematical simulation experiment. The original GNSS data and gyro and acceleration data used in this paper are real flight test data, but the outliers are imposed by simulation. In this way, the verification method is called semi physical simulation verification in this paper.”
MINOR COMMENTS:
1. Line 27. Please replace the word "federal" with "federated".
2. Line 271, 275, 277, Figure 6. There is a suggestion to the authors to replace the GPST time format with the usual UTC representation. First, the GPST time format is integer and there is no week number. And secondly, the presentation of such an excess of information in the figures only makes the timeline more difficult to perceive for the average reader. And as I understood the Major Ticks there is only 20s for the main timeline divisions.
3. Line 375. The word "Lift" came up again
4. It is advisable to use generally accepted terms for the movement of the aircraft, such as "heading and pitch angle, roll angle" throughout the text of the article.
Author Response
Please see the attachment
Author Response File: Author Response.docx
