The Need for a Standardized Methodology for Quantitative Assessment of Natural and Anthropogenic Land Subsidence: The Agosta (Italy) Gas Field Case
Round 1
Reviewer 1 Report
I have no more comment
Author Response
There are no comments to answer
Regards
Reviewer 2 Report
Dear authors,
few minor changes are needed. You can see my comments in the attached pdf file.
Comments for author File: 
Comments.pdf
Author Response
Dear Reviewer,
the point-by-point response is provided in the attached pdf file.
Regards
Author Response File: Author Response.pdf
Reviewer 3 Report
Generic comments:
The paper is not well written. A complete revision of the English form by a native English speaker is mandatory.
The paper is generally quite confusing. In particular in Section 3 is very easy to totally loose the train of thoughts. I suggest to restructure this part of the text in a more schematic way.
The figures are poorly made. I suggest the authors to put more efforts and attention to details in preparing all the figures. This will help in making them more clear and easy to read.
The manuscript do not provide any new scientific innovation: even if a detailed description of the methodologies used to process the SAR images is not provided, the approaches used are in a broad way already well known by the scientific community; the authors do not provide any new information, explanation of the causes or any other kind of information useful to understand the subsidence phenomena occurring in the study area; the results obtained by the authors or the ones provided by the different authorities are not described properly and is not even clear what is the purpose of all the presented comparisons.
As briefly written in the text, in this paper the authors want to raise the attention to the necessity of a standardized procedure to calibrate and validate the InSAR results. This necessity is already well known since many years and in the text nothing new is proposed to address this.
The entire manuscript seems, in my opinion, more a technical report than a scientific paper. For this reason, I do not recommend its publication in this journal.
Specific comments:
Can the authors provide more details about how the different working groups have, during the different comparisons and calibrations, accounted for the different geometries of the InSAR and GPS data, the first obtained along LOS and the second along the vertical direction? This is of critical importance even considering the need to obtain the most reliable results possible.
Line 70: please provide a brief description of the differences between the used datasets.
Line 82. this statement is not true. Inaccuracies in the satellites orbits bring long-wave phase contributions (ramps) in the interferograms. This effect is generally minimized by using precise orbit files and ground control points with known velocities.
Will be useful to prepare a section in which are summarized the characteristics of each different dataset analysed by each institution and remove them from Section 3.
Lines 211-214: how is the comparison between the datasets processed by the different institution made? I am assuming that slightly different processing parameters, reference points and algorithms used have a strong impact on the number and distribution of the detected InSAR points. Is the value reported for the differences of 5-10 mm/yr just a “qualitative” observation?
Figures 5 and 6. The colour scale used to classify the InSAR velocity map should be the same as the one used in Figure 3.
Figure 7: in (a) (better to put the “a” symbol in the figure not as text under it) there is no black line related to the Smarlacca CGPS data.
Line 297: Do you mean “15 cm”?
Line 327: this statement is wrong. The orbital errors produce long-wave phase contributions.
344: the sinking of individual structures or infrastructure is still “land subsidence”. How the anomalous points were removed?
Line 484-487: this is already known since many year. No new ideas or propositions are presented in this work to address this issue.
Author Response
Dear Reviewer,
the point-by-point response is provided in the attached file
Regards
Author Response File: 
Author Response.docx
Reviewer 4 Report
I think the paper is worth to be published, although a bit over-wordy and with really too much references. The paper highlights the tragic situation that a company in Italy has to face with when it has to ask for permission of exploiting natural subsurface resources and land subsidence is a key issue to be accounted for. On a side the company has the capability to establish and manage its own GNSS network, which is surely more properly located with respect to the production wells and more reliable than those managed by public entities because of a prompter management of the possible out-of-orders. On the other, the public authority, who forces by law the private company to establish and monitor land subsidence, develops its own reference network on a much larger scale (hence generally less accurate than the specific-site one), and provide its own subsidence quantification. Obviously, the two maps are not completely consistent, although in this specific case study the SAR-based analyses have been developed for Eni and ARPAE by the same company (I know this personally).
I suggest the authors to add also the PS maps developed by the regional authority to give a reader the possibility of a direct comparison. Surely, an uplift of 2.5 mm/yr (line 350) is very difficult to imagine in the low-lying peatland where the Agosta field is located.
Author Response
Dear Reviewer,
the point-by-point response is provided in the attached file
Regards
Author Response File: Author Response.docx
Round 2
Reviewer 3 Report
In this revised version of the manuscript, the authors improved both the text and the figures. Only some minor adjustments to the text are required. I do not have any other remarks.
I suggest the authors to check the following publication related to their work:
D. 2017. From ERS-1/2 to Sentinel-1: two decades of subsidence monitored through A-DInSAR techniques in the Ravenna area (Italy), GIScience & Remote Sensing, 54:3, 305-328, DOI: 10.1080/15481603.2016.1269404.
Polcari, M.; Albano, M.; Montuori, A.; Bignami, C.; Tolomei, C.; Pezzo, G.; Falcone, S.; La Piana, C.; Doumaz, F.; Salvi, S.; Stramondo, S. InSAR Monitoring of Italian Coastline Revealing Natural and Anthropogenic Ground Deformation Phenomena and Future Perspectives. Sustainability 2018, 10, 3152.
Author Response
The suggested publications have been cited in the text.
Regarding minor adjustments, it was not possible to respond because it was not indicated where they are requested.
