3DGPR for the Non-Destructive Monitoring of Subsurface Weathering of Sandstone Masonry
Round 1
Reviewer 1 Report
an interesting pilot study raising some useful points about the use of 3DGPR and its potential in buildings analysis. I think definitely worth publishing and will be very interested in future work on larger samples.
Author Response
We thank you for your comments and will be presenting our results clearly in revision, thank you.
Reviewer 2 Report
The paper describes an interesting noninvasive approach employing 3D GPR to evaluate the internal structure of a stone wall, which can be significant for pathologies diagnosis.
The paper is well written, stating the objectives clearly and the model proposed based in the interpretation of results, is well justified and convincing.
The overall impact of the work in community is considered important especially in the cases that specific conservation actions have to be planed.
The manuscript can be publishable in particular after considering the following main comments:
In particular the processing chain is not well described, so it is not clear the accuracy (wanted/achieved). On other hand the approach used is based in the detection and location of features along depth, revealed in a serie of slices of 3D-GPR models acquired with different frequencies. However the sections that supports the method are shyly shown on an barely visible panel of figure 4. Is necessary to show a figure that clearly represents all time slices (3.5, 5, 8, 11 and 15cm ) considered, of the 3D GPR models of the 3 antennas (1.2, 1.6 and 2.3 GHz).
Minor issues
Figure 1- The left panel with map location of Belfast is not visible. In the church plan of the right panel it´s missing the numeric value on the scale label.
Line 137 where is Figure 3B is 3A.
Author Response
The limited processing is now described
Figure 1 is now corrected – thanks for spotting this.
Figure 3A and 3B now corrected.
Reviewer 3 Report
Review of 3DGPR for the Non-Destructive Monitoring of 2 Subsurface Weathering of Sandstone Masonry
Generally – would feel more comfortable of the results if an undamaged wall showed fewer “anomalies” or the phase of the anomalies (differences in solid rock reflections) are different than the dry rot of the damaged stones. Either by further experiment or by specific reference.
Do we know that each rock in the wall is a single course thick (we have a map of the surface rocks which is find for a single course, but there are interior rocks we don’t see, they don’t have to line up with surface map).
Page 118 – 119 – authors should attempt to explain what the interpolation is based on generally. From Mala or from what they see in the results.
Page 134 – how does the plastic sheet help the analysis? Because it allows moving the antenna along straight lines and same paths between antenna change outs? It keeps the antenna at same elevation in relation to wall surface or lack of surface?
Page 147-148 – This justification should be backed up a little more, since it is the bases of the entire article. What references say that this is true?
Page 212-213 – Would need a reference that showed that a deteriorated wet rock has same signal as a solid wet rock. I would think more moisture would be in the deteriorated rock than cores of sound rocks. I’m OK with the idea that areas that stay wet don’t deteriorate as much as alternating areas, but that is not what the sentence says.
Page 270-271 – from the traces, I think you should be able to make a guess at if it sound stone or deterioration.
It would be worth briefly repeating a bit of the how deterioration is identified in traces from previous article to let new readers know its not just areas of difference. https://pure.qub.ac.uk/portal/files/147325603/Voids.pdf
Author Response
Responses to Reviewer 3
These are excellent and detailed comments which we appreciate.
The authors note that the reviewer states that they would be more comfortable if undamaged wall sections revealed less anomalies. This wall has been in place within the urban environment for over 100 years and as a result there is no undamaged section. Instead, it is better to consider the upper less weathered section as being in better condition than the more deteriorated middle. The authors note that this confusion is a result of terminology they utilised and have made adjustments to the text to clarify this point.
Reviewer is exactly right – The study focuses on the condition of the visible stones as the interior material fill is fine rubble based. Given the nature of this material, returns beyond the initial blocks are not interpretable due to their complexity and the resolution of return. For this reason, the focus of the paper is the condition of the visible layer of stones. The authors acknowledge the oversight and have added to the paper to clarify this point.
118-119 – This is a very good point, we are dependent on the Mala software, so have added a line to this effect and that in another study, deriving the raw XYZ data and testing our own interpolations could be done.
147-148 – many of the cited authors comment on how to interpret such historic features, so we have cited the two that are relevant.
212-213 – I don’t think we say that wet rock would have the same dielectrics as dry: it is likely that all the structure is damp, but that the weathered rocks have increased moisture content – hence they show up, either from weathering and thus increased clay content, air-permeability or moisture ingress into permeability – very likely a combination of all three, but this is conjecture.
270-271 – we do exactly this and interpret the traces in terms of sound vs unsound stone.
Our previous article is cited and indeed we have used this to show the power of the 3DGPR outputs: as reference [11]: Johnston et al (2018) used 2DGPR, we should not repeat this work, but have made sure the reader can see how this (current) work builds upon that previously published.
Again, we thank the reviewers but especially yourselves for bearing with us.
Round 2
Reviewer 3 Report
All reviewer comments address to our satisfaction.
