Geophysical Surveys for Archaeological Research in Urban Areas: The Case of the Roman Theatre in Padua
Round 1
Reviewer 1 Report
Comments and suggestions
The paper describes a geophysical approach by ERT and GPR methods applied on the Roman theatre of Padua. The authors carried out several ERT sections and GPR profiles in order to define the presence of buried structures and the dimension of the theatre.
The paper is well organized. Anyway, the geophysical results have to be improved in terms of images and interpretations. I suggest to try to merge the ERT and GPR images in order to define the correlation between the resistivity anomalies and the reflections coming from the buried structures.
I suggest making a 3D image with all the inverted ERT profiles. A 3D resistivity image could help the readers to follow the described interpretation in the Results chapter.
I suggest to include some symbols in the image in order to associate the interpretated buried structures with some indications on the figures.
The GPR results highlight several reflections, could you try to make some interpretation on them or they are correlated only with utilities?
How you estimated the em velocities and I suggest to write in the text this value for the used migration.
Comments on Figures:
Figure 7: The depth and X meters are too small. I suggest to improve them.
Figure 8: The radargrams seems not useful for the aims of the paper. May be it is better to use a 3D image of ERT as figure 8.
Author Response
We are grateful to the reviewer for the constructive comments.
We have tried to improve the text and images.
However, the request for the inclusion of the ERT images in 3D could not be fulfilled.
Finally, we believe it is methodologically correct to show that GPR in this context does not work, so we decided not to delete the related images whose fonts, however, are not editable. It is necessary to download the high-resolution image for more detail
Reviewer 2 Report
No correction has been made to the text. The presentation and study of the drawings of the 1700s concerning the remains of the theater is appreciable, fundamental for a correct interpretation of geophysical investigations. It would be helpful, as well as correct from a methodological point of view, to elaborate a figure in which the results are georeferenced (slices and profiles of ERT and georadar), i.e. as a basis the same as fig. 4 could also be fine.
Author Response
We are grateful to the reviewer for the positive comments on the paper. We have, (as suggested), improved the images in Fig. 4 and included more quantitative details on the intersections with the ERT-GPR lines and the archaeological structures in Figure 7.
In additional materials we include a file containing the coordinates (Gauss Boaga West) of each of the most significant ERT-GPR lines and the maximum extents of the cross resistive anomalies and the radial walls with the lines L1, L2, L3.
Reviewer 3 Report
The great merit of this paper is to combine two geophysical methods and these with data from old cartography, although this latter aspect could be better explored. Similarly some results could be better substantiated such as the interpretation of the overall diameter of the theatre. It is not convincing enough that the diameter was around 114 m, considering that there were often other structures attached to the theatres (small temples, peristyles etc), which supported but were not part of the building. Finally Fig. 2 could be more focused on the remains of the Roman theatre which, being the main subject that justifies this photo, occupy a small part of the picture. Finally photo 2 could be more focused on the remains of the Roman theatre which, being the main subject that justifies the photo, occupy a small part of the picture.
In general, the work is of scientific interest, since it adds information to the little that is known about the Roman theatre of Padua.
Author Response
We are grateful to the reviewer for the critical comments that allowed us to improve the text, figures, including more details on the theater, geophysical evidence, and excavation. We agree that it will be necessary (as pointed out in the conclusions) to carry out further geophysical measurements, which an archaeological excavation should necessarily match before validating what is only preliminarily assumed here about the maximum extent of the theatre.
Reviewer 4 Report
Article
Geophysical surveys for archaeological research in urban areas: 2 the case of the Roman Theatre in Padua
General Comments:
1) The gained results in the abstract section is hazy and not clear
2) Abstract in need to be clear, rewritten, and quantitative
3) There is no detailed geological background about the investigated site
4) The authors expected the attenuation of GPR waves throughout the investigated site, why did not utilize another geophysical technique such as gradient magnetic survey.
5) Where is the produced map of the structures of the theatre from the excavation project at 2017?
6) Legend in figure 4 not clear at all
7) Lines (226-229): although the total length of ERT profiles are differs from 35.3 to 23.5 meter, but the authors say the depth of investigation is the same ?
8) GPR records acquired by antennae frequencies 400-900 Hz. Why the authors considered GPR records of 400 Hz?
9) I advise the authors to present the GPR records of frequencies more than 400 Hz in the current study.
10) Figure 6 did not show the used GPR instrument
11) Lines (285-290): the authors said "the GPR produced disappointing results due to the strong signal attenuation associated with the type of soil covering the remains of structures in this area.", Why use GPR, you know this problem firstly!
12) The titles of axis of GPR records are not clear at all (figure 7)
13) All ERT profiles have a range of resistivity 0.6-2.5 Ohm.m, there is no any abrupt increase or decrease in resistvity values. So there is any observed anomalies
14) The titles of axis of GPR records are not clear at all (figure 8)
15) In Line (345), authors said "poor mutual contrast in electrical properties", and in lines (285-290), authors said " the GPR produced disappointing results due to the strong signal attenuation". Where is the manuscript?
16) Where is the geophysical measurements conducted in 2017?
Author Response
REPLY: We are grateful to the reviewer for his heavy, and in some respects not clearly constructive review of the paper, which nevertheless allowed us to improve some specific points that certainly benefited from this revision.
We feel that some comments need a pointed response that touches on the basics of geophysical theory and practice that are best clarified and of which we are quite certain.
Below are the point-by-point responses to the comments:
1 - 2) The abstract has been rewritten and improved
3) Details on the known geomorphology and hydrogeology of the area with relevant literature references have been added
4) Prato della Valle is located (as mentioned) in the middle of actual urban centre of Padua with high magnetic and electromagnetic noise...we apologize for not having made this detail clear enough, which we imagine would have led to avoid suggesting the alternative use of the magnetic (gradient) method in this context even given the depths of the described and hypothesized archaeological structures (about 3 m). Furthermore, we apologize for perhaps mischaracterizing the geological data known a priori and the fact that we did not know instead the nature (later revealed to be conductive) of even part of the sediments covering the structures. This is why we decided to use GPR and ERT measurements.
5) In 2017 the emptying and cleaning of the canal and the excavation project studied only an already known part of the theater submerged in the canal. The caption of the image in Fig. 4 gives The details about the part studied in 2017 in relation to the geophysical surveys.
6) The legend in Figure 4 has been removed and replaced with the description given in the caption.
7) As explained in the text some of the lines are 35.5 m long in total, but a roll-along between two lines of 48 electrodes with overlapping of 24 electrodes between two consecutive lines of the same initial length was performed to avoid holes in the survey. As the reviewer will be aware this results in the final survey depth being related to the actual length of the initial lines thus 23.5 m and the same survey depth at the end.
8-9) having used a dual frequency 400-900 MHz system automatically this produces two sections. However, given the depths of interest (3 m) and the effects due to noise (ground and attenuation) then actually recorded in the field obviously the 900 MHz section was of no interest for the purposes of this study. We therefore consider it unnecessary to present these results. We have included an appropriate commentary describing what is presented here.
10) Absolutely yes, this is the IDS RIS Hi-mod dual frequency system that supports minimum 1 up 4 parallel antennas...In any case we replaced the figure 6
11) see comment 4. In any case it was one of the most suitable systems for these urban surveys
12) It is possible enlarge the image. we cannot automatically change the font
13) The range of data is in Log10 of resistivity...Please check it.
14) see answer 12)
15) This comment is apparently not pertinent. The two cited comments refer to two different observations, one on archaeological structures and the other on soil.
16) In Figures 4, 7,8, 9--what is the reviewer referring to?
Round 2
Reviewer 4 Report
Major of the required modifications were done
