TLS Measurement during Static Load Testing of a Railway Bridge
Round 1
Reviewer 1 Report
The paper investigates the accuracy of railway bridge deformation estimation using a terrestrial laser scanner.
Three procedures for deformation estimation from TLS data are investigated: B&W markers detection, point cloud differentiation, and mesh surface differentiation.
The procedures are compared with traditional methods: tacheometry and precision levelling.
The authors draw several conclusions from their investigation, which may help practitioners in the choice of the deformation estimation method.
Overall, the paper is well-structured. Tables like Table 1 are useful to keep track of the many procedures analyzed in the paper. However, the English of the paper should be improved. A few sentences are long and convoluted.
The contribution of the paper with respect to the state of the art is unclear. This is not the first paper which uses a TLS to compute deformation of a bridge under load. The contribution must be pointed out explicitly in the introduction.
Some related work is cited in the introduction, and then again at the end of each subsection in Section 3. The relation of the relate work to this paper is unclear. The paper should be compared explicitly with the related work. Are they using a method from the cited paper? Are they refuting the cited results? Are they confirming them? Are they doing something better or different?
In Section 2.4, the point cloud pre-processing method is described. Standard point cloud filters from CloudCompare and Geomagic Wrap software were used. The authors should expand the description of the filters and report their configuration parameters, to allow others to reproduce the results, even if/when the software becomes unavailable.
Similarly, in Sections 3.2 and 3.3 point cloud and mesh differentiation are carried out, but the method is not described.
Author Response
Dear Sir or Madam,
Thank you for your knowledgeable review of my research. All comments have been included in the article. In attachment I send a cover letter to explain point-by-point the details of the revisions in the manuscript and my responses to your comments.
I hope that I introduced my remarks rightly and adequately.
Sincerely,
--
Eng. Pelagia Gawronek, PhD
Department of Land Surveying
University of Agriculture in Krakow
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Research contribution by the paper:
The paper describes a concept for the measurement involved three methods of determination of the displacement during the static load test of the bridge. The first one was precise levelling, the second was precise reflector less tacheometry of a controlled point network, and the third one, terrestrial laser scanning of the railway bridge.
The conclusion of this paper is that TLS measurement during the static load test of the railway bridge facilitates identification of displacement with the accuracy of ± 1 mm regardless of the post-processing method but is still behind precise surveying methods. The authors stated that TLS measurement should be used as an auxiliary tool to supplement traditional precision levelling.
Comments on the contents of the paper:
1. A Figure of the actual appearance of the railway bridge is missing in the paper.
2. In my opinion, the MAE errors [m] and RMS [m] of the order of 1mm are unreliable because they can be affected by errors such as rounding numbers. Such errors (in my opinion) should, however, be greater.
3. Figure 2 shows that there were only two measuring stations for TLS. In my opinion, this is not enough.
4. However, there is a lack of such a "specific" summary and the answer to the question: what are the displacements (significant / non-significant, causing threat / non-threatening) and how they are to the standards established for such constructions. Are the results within acceptable limits?
5. In my opinion, there should be a different scientific goal at work and a concrete answer. Because the conclusion that In my opinion, there should be a different scientific goal at work and a concrete answer. Because the application that is not enough.
Questions to authors:
Were there any studies using accelerometers on this railway bridge?
Decision
The idea of this paper is good, but needs some corrections. I apply for admission the paper to the publication but after the amendments.
Author Response
Dear Sir or Madam,
Thank you for your knowledgeable review of my research. All comments have been included in the article. In attachment I send a cover letter to explain point-by-point the details of the revisions in the manuscript and my responses to your comments.
I hope that I introduced my remarks rightly and adequately.
Sincerely,
--
Eng. Pelagia Gawronek, PhD
Department of Land Surveying
University of Agriculture in Krakow
Author Response File: Author Response.pdf
Reviewer 3 Report
Review of the paper: TLS measurement during static load testing of a railway bridge by P. Gawronek and M. Makuch
The article describes an interesting application of high-quality surveying methodologies for the deformation monitoring of a bridge in Poland. In general this paper can gain a lot of audience. However there are some significant issues that they should be clarified to be re-written in order to be published.
Let me point out my findings:
1. Section 2.3 Page 4, lines 167-183
The authors should describe in more details the network of the precise levelling and thacheometry: Hoe many points, type of constriants accuracy of the observations, realiability analysis etc.
2. Page 5, Lines 200-203 (see also Table 2, Page 6, Line 227)
The height of the reference spheres: How the height was reduced to the center of the sphere? Do the know precisely the radius of the sphere? If so, how accurate is the radius of the sphere determined?
3. Page 7, Line 258, Equation (1)
The authors just point out a difference of the two different height information sources. This is not reliable at all. One should also apply a test of significance (Ho: The difference are not statistically significant, Ha: The difference are statistically significant). It is possible that an outlier could distort the derived information. Tip (using the normal distribution for the test of significance).
e.g.
abs(dvi_Leb-dvi_TLS) / variance (δdv) < z (a/2)
The authors should also explain the other statistical characteristics (lines 259-261)
4. Page 7, line 269
What does the term MAE mean? There is no explanation
5. The use of the Kolmogorov-Smirnov test
First of all the authors do not give a clear and concise explanation why they are using this test. For example, I find that the t-test could fit better to this type of study, especially for deformation studies. Did they also test another type of test? In addition, the authors do not give any details about this test. This could immediately mislead the reader and weaken the quality of their work.
6. Page 8, Table 4
This Table causes a big confusion: First of they put the KS test in to an element of the table which is rather annoying for the reader. On the top of that, they do not explain the level of confidence and the rejection criteria. Following the remark 4, the authors should re-write (and of course justify) the whole procedure. The Table 4 is completely confusing.
General concerns
· Did the authors implement a kind of 1-D transformation between the height derivation methods? I strongly believe that the transformation using
a) a constant bias term or
b) level equation or
c) a polynomial could offer a good picture of the reliability. This is really important for the TLS measurements.
· Some of the references are in Polish. The authors should translate it in English with the notification (in Polish).
Author Response
Dear Sir or Madam,
Thank you for your knowledgeable review of my research. All comments have been included in the article. In attachment I send a cover letter to explain point-by-point the details of the revisions in the manuscript and my responses to your comments.
I hope that I introduced my remarks rightly and adequately.
Sincerely,
--
Eng. Pelagia Gawronek, PhD
Department of Land Surveying
University of Agriculture in Krakow
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
No comments
Author Response
Dear Sir or Madam,
Thank you for your review and checking of editing of my research. The paper was verified by professional language editing service Swolany. In attachment I send certificate to confirm the quality of translation.
I hope that language editing of my paper is correct.
Sincerely,
--
Eng. Pelagia Gawronek, PhD
Department of Land Surveying
University of Agriculture in Krakow
Author Response File: Author Response.pdf
