Performance Assessment of Structural Monitoring of a Dedicated High-Speed Railway Bridge Using a Moving-Base RTK-GNSS Method
, Weiping Jiang 3, Wei Xuan 1,4,*, Dongsheng Xu 1,2, Jian Yang 1, Lihua He 5 and Jun Ma 6
Round 1
Reviewer 1 Report
This work used a moving-based station at the bridge tower to tackle the blocking problem in position monitoring. The resolution is better than 4 mm at a sampling rate of 5 Hz. Some issues should be solved before publishing:
1. Is the moving-based RTK-GNSS observation model proposed by the author? If not, please cite relevant literature.
2. In the case of a moving-base baseline (JCZ3), should the reference station REF0 be used? Besides, it seems like the obtained displacement is relative to JCZ3 when adopting it as the reference station.
3. The figure name and in-text citation are incorrect. For example, Fig. 2 is cited as Fig. 3 in Line 243.
4. A mistake exists in the description of Fig. 5, wherein the Z direction is represented by the green line, not blue.
5. In Fig. 11, the estimated displacement is compared to the result of a model. More details, especially the input, of the model, should be explained.
Some abbreviations of technical phrases, for example, the PDOP, should be explained.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Manuscript ID: remotesensing-2395147
Title: Performance assessment of structural monitoring of a dedicated high-speed railway bridge using a moving-base RTK-GNSS method
Authors: Ruijie Xi, Weiping Jiang, Wei Xuan, Dongsheng Xu, Jian Yang, Lihua He, and Jun Ma
In this manuscript authors use the moving base Real Time Kinematic – Global Navigation Satellite System (RTK-GNSS) methodology to realize the relative precise positioning of some semi-permanent GNSS stations, so as to improve the availability of GNSS in the application of bridge structure health monitoring. Moreover, the moving-base RTK-GNSS model is derived and verified by GNSS monitoring data of Ganjiang river dedicated high-speed railway bridge.
The paper represents an interesting application of GNSS to the real-time monitoring of a bridge but in the present form cannot be accepted for publication in Remote Sensing journal. Some indications aimed at improving this work follow:
1) At line 214 of the section “2.3. Parameter estimation and ambiguity resolution” the LAMBDA method to search and fix the ambiguities should be described in more details adding some necessary references.
2) At line 217 of the section “3.1. Ganjiang Bridge and GNSS data description” authors should describe better the concept of span arrangement, the sentence needs rearranging and widening to be clearer.
3) At line 219 and 225, 225, Authors should spend some more sentences to describe with more details the structural health monitoring system installed in the Ganjiang river bridge.
4) At line 229, 230, of the same section, it is not clear why authors chose these four positions to set monitoring stations. In my opinion it would be better to use other monitoring points uniformly distributed throughout the body of the bridge and to carry out optical measurements with distance meters to verify the displacements.
5) At line 239, authors should explain better the choice of 5Hz of sample rate of the GNSS stations, in my opinion should be better to use the highest frequency of 1Hz.
6) At lines 291 to 293 of the section “3.4. Displacement and vibration monitoring” the authors talk about previously described GNSS data processing methods, but I think that the processing of the GNSS data should be described in details adding some information like the software used, the modelling of the GNSS bias etc. etc..
7) At line 303 of the same section in the corresponding Figure 5, authors are showing the position time series of components X, Y, Z. Authors should provide some type of geo-referencing, and position time series should be expressed in North, East, Up (vertical) components.
8) From line 322 to line 338 of the same section “3.4. Displacement and vibration monitoring” the authors explicitly refer to figure 8, therefore I think it is better to move the Figure 8 after this section.
9) At line 363 of the section “4.1. Displacement estimation” the authors mention the term of deformation, but while the displacement has the dimensions of a length (m or mm), the deformation is dimensionless being by definition the derivative of the displacement itself, , the authors should clarify this concept.
10) At lines 459, 460 of the section “5. Conclusions” it would be better to restructure and expand this sentence to make it clearer.
Therefore, based on what has been described above, I suggest reconsidering this work after a major revision process.
Manuscript ID: remotesensing-2395147
Title: Performance assessment of structural monitoring of a dedicated high-speed railway bridge using a moving-base RTK-GNSS method
Authors: Ruijie Xi, Weiping Jiang, Wei Xuan, Dongsheng Xu, Jian Yang, Lihua He, and Jun Ma
In this manuscript authors use the moving base Real Time Kinematic – Global Navigation Satellite System (RTK-GNSS) methodology to realize the relative precise positioning of some semi-permanent GNSS stations, so as to improve the availability of GNSS in the application of bridge structure health monitoring. Moreover, the moving-base RTK-GNSS model is derived and verified by GNSS monitoring data of Ganjiang river dedicated high-speed railway bridge.
The paper represents an interesting application of GNSS to the real-time monitoring of a bridge but in the present form cannot be accepted for publication in Remote Sensing journal. Some indications aimed at improving this work follow:
1) At line 214 of the section “2.3. Parameter estimation and ambiguity resolution” the LAMBDA method to search and fix the ambiguities should be described in more details adding some necessary references.
2) At line 217 of the section “3.1. Ganjiang Bridge and GNSS data description” authors should describe better the concept of span arrangement, the sentence needs rearranging and widening to be clearer.
3) At line 219 and 225, 225, Authors should spend some more sentences to describe with more details the structural health monitoring system installed in the Ganjiang river bridge.
4) At line 229, 230, of the same section, it is not clear why authors chose these four positions to set monitoring stations. In my opinion it would be better to use other monitoring points uniformly distributed throughout the body of the bridge and to carry out optical measurements with distance meters to verify the displacements.
5) At line 239, authors should explain better the choice of 5Hz of sample rate of the GNSS stations, in my opinion should be better to use the highest frequency of 1Hz.
6) At lines 291 to 293 of the section “3.4. Displacement and vibration monitoring” the authors talk about previously described GNSS data processing methods, but I think that the processing of the GNSS data should be described in details adding some information like the software used, the modelling of the GNSS bias etc. etc..
7) At line 303 of the same section in the corresponding Figure 5, authors are showing the position time series of components X, Y, Z. Authors should provide some type of geo-referencing, and position time series should be expressed in North, East, Up (vertical) components.
8) From line 322 to line 338 of the same section “3.4. Displacement and vibration monitoring” the authors explicitly refer to figure 8, therefore I think it is better to move the Figure 8 after this section.
9) At line 363 of the section “4.1. Displacement estimation” the authors mention the term of deformation, but while the displacement has the dimensions of a length (m or mm), the deformation is dimensionless being by definition the derivative of the displacement itself, , the authors should clarify this concept.
10) At lines 459, 460 of the section “5. Conclusions” it would be better to restructure and expand this sentence to make it clearer.
Therefore, based on what has been described above, I suggest reconsidering this work after a major revision process.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 3 Report
Although the subject of GNSS data optimization is well known and widely used in the literature, it can still be interesting in terms of the application results that can be obtained with the methodology proposed in the note.
From a general point of view, it is necessary to carefully double check the reference of the figures to the text, as there are several errors.
In general, for the reasons set out above, it should be given more weight to the application part by eliminating all the theorical parts (already well known in the literature), focusing instead on the explanation of the proposed method (arguing in detail, in particular, the subparagraph 2.3 which expressly concerns the proposed method).
As regards the results it is necessary to carefully recheck all the values reported in the various results tables because they seem too optmistic, as that the final sentence reported from line 460 to 462.
In my opinion, the quality of English Language seems acceptable, even from a technical point of view even if, sometimes some sentences must to be improved and/or reformulate.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 4 Report
It is a very practical topic area. My main problem with this manuscript is the lack of verification of the results. For example, the authors claim that they can capture 2mm movement of the moving carrier. How was this claim verified. Typically we would use some independent measurement technique.
The manuscript is a bit confusing because the figure references appear to be misplaced. For example, "Figure 8 gives a high-speed train..." should refer to Figure 7. Also, the references to Figures 10 and 11 (time series) should really refer to figures 9 and 10.
The authors indicate that the sampling rate is 5 Hz (line 239). Can you elaborate that this sampling rate is in fact sufficiently high to capture the effects of a fast moving train? Normally for this type of dynamic applications we use dataloggers with very fast sampling rates.
The trend of displacement results is intuitively correct but it hard to get any appreciation for the actual numbers without knowing more about the bridge. Can you provide some additional details on the bridge design and perhaps some statements from bridge designers to the effect that the magnitudes measures by the authors are in line with the expected deformations under these particular loading conditions?
Conceptually, the idea advanced by the authors appears to very sound. The problem is to prove the claimed accuracy. This part of the manuscript should be expanded on. There should be more input from bridge designers in this manuscript.
Minor English edit is recommended.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
None.
Author Response
Many thanks.
Reviewer 2 Report
Dear Authors of manuscript remotesensing-2395147,
After completing the revision process of this work the manuscript was really improved by authors responding positively to the targeted advice that I’ve indicated in my review report. Therefore, I suggest accepting this manuscript for publication in Remote Sensing Journal in the current and revised form.
Author Response
Many thanks.
Reviewer 3 Report
The paper has been improved.
However, no response was given to my previous two observations that I report:
"In general, for the reasons set out above, it should be given more weight to the application part by eliminating all the theorical parts (already well known in the literature), focusing instead on the explanation of the proposed method (arguing in detail, in particular, the subparagraph 2.3 which expressly concerns the proposed method)".
"As regards the results it is necessary to carefully recheck all the values reported in the various results tables because they seem too optmistic, as that the final sentence reported from line 460 to 462."
I continue to remain of the opinion that despite the observations reported by the reviewers, the two points indicated should be verified and implemented
Author Response
Many thanks for the comments.
We have shortened the theorical parts in the manuscript, and left the key information of the method. The detailed concerns in the data processing have been given in section 2.3.
As for the values in the Table 3 and Table 4, the GNSS observations can precisely capture the movement of the towers, and the precision could achieve to about 1 millimeter. Thus, the RMSs of the bending displacement is better than 4 mm. However, the estimates of the amplitude of the vibration signal is about 1 mm, and the residuals are mostly less than 1 mm. Therefore, the RMSs seem too optmistic. The RMSs of the tower amplitudes lower than 1 mm are not shown in Table 4. But the moving-base RTK method could be an alternative scheme to capture the movement and vibration signal when the observation environment of the reference station is poor or equipment failure happened.
