Improving GNSS Landslide Monitoring with the Use of Low-Cost MEMS Accelerometers

Round 1

Reviewer 1 Report

 

The paper reports a simple and better calibration of an accelerometer as inclinometer. Compare to the first submitted manuscript some points have been improved (the English, the quality of the picture…..) but I do believe another round of revisions is still need before acceptance. They should address the points below:

 

It is still very difficult to understand what the part “Integration of accelerometers into prototype monitoring stations” brings to the paper. A cost effective demonstrator has been made by assembling together a GNSS antenna and an accelerometer. It is very nice but what type of measurements have been performed with it? Does it meet the requirements of the monitoring needed at the location in Piedmont? Further the calibration was performed on 8 accelerometers. It would be interesting to see those results. Put this will find its place in another section. The authors mention that the proposed method is low cost. The total process described in section 4.1 do take up to 1 and ½ hour (15 minutes/face). I assume it requires an engineer to do the job? Or can the calibration be automated? Then it would become low cost. Figure 6 needs to be improved. Please report what is plotted on the axes. Put (Rx) residual in the legend of the figure. If Figure 6 is plotted vs time than how the tilt residues behave? By the way why it gets worse after 657 (but once again what is this value?)

Author Response

Dear Reviewer 1,

first of all thanks for the important advice and careful review: let's try to answer hoping to improve the understanding of the paper. Below are the answers.

The paper reports a simple and better calibration of an accelerometer as inclinometer. Compare to the first submitted manuscript some points have been improved (the English, the quality of the picture…..) but I do believe another round of revisions is still need before acceptance. They should address the points below:

 It is still very difficult to understand what the part “Integration of accelerometers into prototype monitoring stations” brings to the paper. A cost effective demonstrator has been made by assembling together a GNSS antenna and an accelerometer. It is very nice but what type of measurements have been performed with it? Does it meet the requirements of the monitoring needed at the location in Piedmont? Further the calibration was performed on 8 accelerometers. It would be interesting to see those results. Put this will find its place in another section. The authors mention that the proposed method is low cost. The total process described in section 4.1 do take up to 1 and ½ hour (15 minutes/face). I assume it requires an engineer to do the job? Or can the calibration be automated? Then it would become low cost. Figure 6 needs to be improved. Please report what is plotted on the axes. Put (Rx) residual in the legend of the figure. If Figure 6 is plotted vs time than how the tilt residues behave? By the way why it gets worse after 657 (but once again what is this value?)

We have improved figure 6. For the proposed discussion on the accuracy and use of accelerometers we have introduced section 4.2. The results of the calibrations of the 8 accelerometers are then reported and discussed in section 4.2

Thank you for taking the time to read our paper: we have appreciated your helpful suggestions.

Sincerely,

The Authors

Author Response File: Author Response.docx

Reviewer 2 Report

Basically I found the ms need serious improvements in several parts before to be considered ready for publication. The description of the monitoring techniques used for landslide monitoring is really poor and needs to be improved. Additional references need to be included in this part, but also to support th equations used. Conclusions sections should be improved adding some comment on what rotations could have instrumental origin or could be associated to the landslide movements, and if their origin could be identified using the MEMS accelerometers. Really I would like to see clearly described what is the improvement given by using these sensors.

Therefore I recomend MAJOR REVISION for this ms.

OTHER COMMENTS.

1) Abstract should be revised after correction of the ms.

2) Introduction. Lines 28-35. References should be added here. I think the authors should read the papers

Fernández, J., F. J. González-Matesanz, J. F. Prieto, G. Rodríguez-Velasco, A. Staller, A. Alonso-Medina and M. Charco, 2004. GPS Monitoring in the N-W part of the volcanic Island of Tenerife, Canaries, Spain. Strategy and results. Pure and Applied Geophysics, vol 161, nº 7, 1359-1377, doi: 10.1007/s00024-004-2509-2.

Bru, G., Escayo, J., Fernández, J., Iglesias, R., Mallorquí, J.J., Iglesias, R., Sansosti, E., Abajo, T., Morales, A., 2018. Suitability assessment of X band A-DInSAR techniques for monitoring site scale slow moving landslides: The Leintz Gatzaga (Guipúzcoa, Spain) test-case. Remote Sensing, 10, 936; doi: 10.3390/rs10060936.

and references on them, to improve the description of the monitoring methods used for landslides as well as for the use of poles, citing other alternative options used by other authors in similar studies.

In lines 45-53 I consider some references should be added to support the text.

3) Figure 1 must be improved. It is really difficult to read the text. Maybe changing back color in the background by grey could be fine.

 

4) I consider some references supporting the equations (1) to (3) used in section 2 should be necessary, mainly if they are not original from the authors.

 

5)I think text in lines 100-103 is too obvious and could be deleted.

6) Lines 104-129, please cite references associated to equations clearly or made note what are originals from aouthors.

7) line 138. Please give more information.

8) Line 142. Last sentence, has been tested and verified?

9) Please include conclusions in a more especific way, explaining in detail what is the important novelty of using these sensors in the monitoring of landslide, what can be obtained using MEMS accelerometers which can not be obtained (or at least not at so low cost) without these sensor...

Text now is too general. What is the accuracy in the field of the sensors?

 

 

Author Response

Dear Reviewer 2,

first of all thanks for your important advice and careful review: let's try to answer hoping to improve the understanding of the paper. We have greatly expanded the bibliography. Below are the answers.

Basically I found the ms need serious improvements in several parts before to be considered ready for publication. The description of the monitoring techniques used for landslide monitoring is really poor and needs to be improved. Additional references need to be included in this part, but also to support th equations used. Conclusions sections should be improved adding some comment on what rotations could have instrumental origin or could be associated to the landslide movements, and if their origin could be identified using the MEMS accelerometers. Really I would like to see clearly described what is the improvement given by using these sensors.

Therefore I recomend MAJOR REVISION for this ms.

OTHER COMMENTS.

1) Abstract should be revised after correction of the ms.

2) Introduction. Lines 28-35. References should be added here. I think the authors should read the papers

Fernández, J., F. J. González-Matesanz, J. F. Prieto, G. Rodríguez-Velasco, A. Staller, A. Alonso-Medina and M. Charco, 2004. GPS Monitoring in the N-W part of the volcanic Island of Tenerife, Canaries, Spain. Strategy and results. Pure and Applied Geophysics, vol 161, nº 7, 1359-1377, doi: 10.1007/s00024-004-2509-2.

Bru, G., Escayo, J., Fernández, J., Iglesias, R., Mallorquí, J.J., Iglesias, R., Sansosti, E., Abajo, T., Morales, A., 2018. Suitability assessment of X band A-DInSAR techniques for monitoring site scale slow moving landslides: The Leintz Gatzaga (Guipúzcoa, Spain) test-case. Remote Sensing, 10, 936; doi: 10.3390/rs10060936.

and references on them, to improve the description of the monitoring methods used for landslides as well as for the use of poles, citing other alternative options used by other authors in similar studies.

Answ: thanks for the advice: we have integrated the abstract and included in the introduction the recommended bibliography to better clarify the problem. Further bibliography has been introduced (15).

In lines 45-53 I consider some references should be added to support the text.

Answ: we have added an important reference (16)

3) Figure 1 must be improved. It is really difficult to read the text. Maybe changing back color in the background by grey could be fine.

Answ: thanks, we did this

4) I consider some references supporting the equations (1) to (3) used in section 2 should be necessary, mainly if they are not original from the authors.

 Answ: we have added a reference (18)

5)I think text in lines 100-103 is too obvious and could be deleted.

Answ: we did this

6) Lines 104-129, please cite references associated to equations clearly or made note what are originals from authors.

Answ: the reference for 104.129 line is in (12) (see line 123)

7) line 138. Please give more information.

Answ: we have updated the paragraph

8) Line 142. Last sentence, has been tested and verified?

Answ: we have updated the paragraph to make it more understandable. In particular 1g correspond 1000 mV that correspond 90°. Consequently 1°=1000mV/90°=11.1 mV. The RMS=0.24 mV correspond to 1°*0.24mV/11.1mV=0.022°. This is the declared noise of the accelerometer, which has been reasonably verified with the experimental tests

9) Please include conclusions in a more especific way, explaining in detail what is the important novelty of using these sensors in the monitoring of landslide, what can be obtained using MEMS accelerometers which can not be obtained (or at least not at so low cost) without these sensor...

Text now is too general. What is the accuracy in the field of the sensors?

Answ: thanks for the suggestion: given also the similar requests of the other reviewers, we added section 4.2 to explain importance and accuracy in the field. The results of the calibrations of the 8 accelerometers are then reported and discussed in section 4.2. The conclusions are supplemented with some considerations on the use of these inclinometers

Thank you for taking the time to read our paper: we have appreciated your helpful suggestions.

Sincerely,

The Authors

 

 

Author Response File: Author Response.docx

Reviewer 3 Report

This is a valuable submission, carefully prepared and reporting sound experiments on the application of MEMS accelerometers in tilt monitoring in civil engineering. The method is simple and sound and even somehow trivial. Yet the recent influx of cheap sensors makes it possible for the implementation of many simple methods of measurements such as this one.

This reviewer would like to know the answer to the following question: What does it mean "cheap" MEMS sensor in this application with relation to the required monitoring accuracy. Nowadays there are on the market much cheaper acceleration sensors than the 4030 one costing 130 Euro (e.g. those used in cheap drones or smartphones). 

So if possible please include a paragraph answering a question to what extent the applied 4030 sensor is enough accurate for the purposes of the tilt monitoring in this case. Is accuracy 1 degree the actual demand? No need for better accuracy? Could one use cheaper sensors too? It seems that the 4030 sensor is at least 10 times more accurate than 1 degree demanded accuracy. On the other hand, could one save money choosing a triaxial sensor which costs 20 Euro? Write more about the actual demands in tilt measuring with respect to landslide monitoring so that the application of 'cheap' MEMS sensors is fully justified.

The English language is acceptable, but the text should be double-checked with respect to some minor, typo errors: eg.: 

page 1 line 18 "The use of an MEMS..."
page 1 line 42 "microradiant..."
page 2 line 57-61. No need to write definite article 'the' so many times in repeated words 'The section...'
page 5 line 151 "An example is shown in Table 1, and in Table 2 is the ..." the first word 'is' should not be used.
  

Author Response

Dear Reviewer 3,

first of all thanks for the important advice and careful review: let's try to answer hoping to improve the understanding of the paper. Below are the answers.

This is a valuable submission, carefully prepared and reporting sound experiments on the application of MEMS accelerometers in tilt monitoring in civil engineering. The method is simple and sound and even somehow trivial. Yet the recent influx of cheap sensors makes it possible for the implementation of many simple methods of measurements such as this one.

This reviewer would like to know the answer to the following question: What does it mean "cheap" MEMS sensor in this application with relation to the required monitoring accuracy. Nowadays there are on the market much cheaper acceleration sensors than the 4030 one costing 130 Euro (e.g. those used in cheap drones or smartphones). 

So if possible please include a paragraph answering a question to what extent the applied 4030 sensor is enough accurate for the purposes of the tilt monitoring in this case. Is accuracy 1 degree the actual demand? No need for better accuracy? Could one use cheaper sensors too? It seems that the 4030 sensor is at least 10 times more accurate than 1 degree demanded accuracy. On the other hand, could one save money choosing a triaxial sensor which costs 20 Euro? Write more about the actual demands in tilt measuring with respect to landslide monitoring so that the application of 'cheap' MEMS sensors is fully justified.

Answ: thanks for the suggestion: given also the similar requests of the other reviewers, we added section 4.2 to explain importance and accuracy in the field. The results of the calibrations of the 8 accelerometers are then reported and discussed in section 4.2

The English language is acceptable, but the text should be double-checked with respect to some minor, typo errors: eg.: 

page 1 line 18 "The use of an MEMS..."
page 1 line 42 "microradiant..."
page 2 line 57-61. No need to write definite article 'the' so many times in repeated words 'The section...'
page 5 line 151 "An example is shown in Table 1, and in Table 2 is the ..." the first word 'is' should not be used.
  

Answ: thanks for the reports: we have corrected all the errors

Thank you for taking the time to read our paper: we have appreciated your helpful suggestions.

Sincerely,

The Authors

 

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors have revised their manuscript according to the comments.

The paper can now be accpeted for publication.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The manuscript titled “Low-cost MEMS accelerometers in the monitoring of landslides and structures” proposes using a commercial off the shelf 3-axis MEMS accelerometer for landslide monitoring. An analytical model has been set up for calibrating the bias and scale factor.

The proposed application is the interesting part of the paper, however, the manuscript structure is not clearly showing the details of the work and having many editorial errors makes it even harder to understand the presenting points. The manuscript suffers from several critical limitations that need to be addressed in detail. These are summarized below.

In page 2 and, the capacitive accelerometer description is very confusing and lacks clarity. Descriptions of the piezoelectric effect and electrostatic effect are mixed, and this seems like an error.

In the same paragraph, the authors are mixing the Si properties with Quartz crystal properties and it seems this part needs a careful editorial check. It is not clear why authors present piezoelectricity and piezoelectric properties while using electrostatic sensing.

In page 3, the terminology “capacity” should be “capacitance”!

In page 4-5, the mathematical details of applying the LMS to compute the calibration parameters are missing.

It is recommended to switch the low-quality screenshots with clean and readable data lots. (e.g. Figure 8 & 6)

Reviewer 2 Report

 

The paper reports the calibration of an accelerometer as inclinometer however the title promises monitoring of landslides but beside the calibration of the sensor little is said on its application.

If the authors do wish to resubmit their manuscript, they should address the points below:

Extensive editing of English language is required. The figure style and captions have to be checked. For example in figure 3, it s not possible to read what s on the figure!! Do not use white. The figure caption is also wrong. What is the meaning of the insert in Figure 8? What are a), b) and c) in Figure 7? The format of Table 1 and 2 is not consistent with the format of table 3 and 4!! What is the meaning of the bold highlighted in those tables……… The calibration part on its own can be the subject of a paper. It is very difficult to understand what the discussion part add to the paper. Is Figure 8 saying the measurements are stable? Only in the conclusion there some explanation of the all system (“the inclinations serve to separate the movements 241 of the antenna from the rotations of its support”).