Using Ground Penetrating Radar (GPR) to Locate the Remains of the Jaundole (New Dahlen) Castle Near Riga, Latvia

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear authors,

thank you for the nice reading of your article. It is well written and easily understandable. As I am a geophysicist, I am focusing on the geophysics part of your article and have the following comments. The most critical point is the comparison of timeslices and cross sections, which is not correct.

- Please add the aims of this article at the end of the introduction. They are given in Materials and methods, maybe better move them to the introduction.
- Line 184: Vertical stacking and sampling rate are two different things. Please clarify. And please give a number for the "appropriate" sampling rate.
- Line 188: In which direction was the running average applied? Along each trace with time or horizontally over multiple traces?
- Line 192: How did you correct for topography? Did you move the traces up/down or did you apply a topographic migration?
- Fig. 16. Please mark the location of the cross section in the timeslice. From the yellow and red box I would assume that the cross section is running diagonal across the area, but from the length scale I would assume a "North-south" running profile. In addition, in the cross section everything seems to have a similar reflection strength, but in the time slice this is not visible. Maybe you can enlarge the cross section and reduce the gain slightly in order to see more differences.
- Fig. 17, 18 and 19: same comment as before for Fig. 16
- Fig. 18: I cannot believe that you see all marked boxes in one profile! In that case you would have needed to make a zigzag-line crossing the area. But I saw on the photos that you made straight lines. Please check the connection between timeslice and cross section again. This is valid for all GPR figures!
- Line 554 ff: Please rewrite this paragraph after correcting the connection between time slices and cross sections.
- Line 572: It would be nice to have a figure with the GPR interpretation and historical findings showing the castle in addition to the text.
- Summary and Conclusion: In my opinion the summary can be shortened, as most is pure repetition from text before.

Author Response

Thank you very much for reviewing this manuscript. Please see attached for the detailed responses. 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The contribution you have submitted is of clear value and presents a relevant and timely case study. I believe it deserves to be published after some necessary revisions. The comments below are intended to help improve the structure, clarity, and scientific impact of your manuscript.

Astract: It reads more like a summary of events than a concise scientific abstract. It includes historical details that are better suited for the main text. I suggest something like this :

This study investigates the subsurface remains of Jaundole Castle, a 14th-century medieval fortress located on Dole Island near Riga, Latvia. The castle, which has left no visible surface traces, is known only from historical documents and maps. To assess whether its buried remains could be detected, a non-invasive Ground Penetrating Radar (GPR) survey was carried out across five targeted grids. The results revealed multiple linear and circular anomalies consistent with historical records of the castle’s layout, including possible foundations of walls and towers. These findings demonstrate that GPR, when combined with historical cartographic analysis, can effectively locate and delineate lost architectural features. The integration of historical sources and geophysical data provides a replicable model for the investigation of other completely buried archaeological sites. This work contributes to the development of non-destructive prospection strategies and supports the planning of future archaeological excavations and conservation actions.

The introduction should be revised to include a clear historical and environmental background of the site, explaining why the location is archaeologically important, what transformations it has undergone over time, and why the investigation was conducted there. It should also briefly outline the added value of using Ground Penetrating Radar (GPR)—not in technical terms, but as a non-invasive tool for detecting buried architectural remains.

The research objectives, currently repeated in the conclusions, should be clearly stated at the end of the introduction. For example:
"This study aims to: (1) identify the likely location, layout, and function of the Jaundole Castle through historical sources; (2) evaluate the effectiveness of ground-penetrating radar (GPR) for detecting its buried remains; and (3) determine whether structural elements can be interpreted from GPR data to support future archaeological excavations."

I suggest beginning the introduction with a more structured and contextual opening, such as:
“The historical landscape of Dole Island, located along the Daugava River southeast of Riga, Latvia, hosts the buried remains of two medieval castles: Vecdole and Jaundole…” .

Suggested revised structure of the paper:

1. Introduction
   – Including background, rationale, methodology, and clear objectives.

2. Historical and Iconographic Description

3. GPR Methods
   – Justify the exclusive use of GPR with a sentence such as:
   “Although complementary geophysical methods such as electromagnetic induction or resistivity tomography can provide valuable information, the present study focused on GPR due to its high resolution and proven effectiveness…”
   – Alternatively, this can be stated in the conclusion, emphasizing possible future integration.

4. GPR Results

5. Discussion
   – Including the historical and archaeological implications.

6. Conclusions
   – Summarize in 3–5 bullet points: findings, implications, limitations, and future perspectives.

Additional comments:

• Figures:
  – Consider combining Figures 2, 3, and 4. Since Figures 2 and 3 do not show major differences, one can be removed.
  – Figure 4 should be retained.
  – Move Figure 12 to supplementary material or merge with Figure 13.
  – Add geographic coordinates to Figure 1.
  – Ensure all figure labels and legends are in English, and avoid local language where possible.
  – Use “Grid 1” instead of “grid one” throughout.
  – Consider adding a 3D rendering of GPR time slices to better visualize the spatial distribution of anomalies.

• Textual content:
  – Avoid repeating historical information across multiple sections; consolidate into one well-structured paragraph.
  – Streamline Sections 3.1.2, 3.2.2, and 3.2.4 by retaining only information directly relevant to the geophysical interpretation.
  – The geophysical interpretation should be expanded to include a critical reflection on limitations, uncertainties, and alternative interpretations.
  – Avoid using expressions like “summer 2024”; this is a scientific article, not a fieldwork report. Mention dates only if strictly necessary, preferably in the Methods section.

• Language:
  – The English is generally understandable, but some parts need improvement to clearly express the research aims and findings.

  Suggested key-words: archaeological survey; medieval castle; cultural heritage; historical cartography; Dole Island, Latvia; Riga

   

  m instead of meters

  km instead of kilometers

  MHz instead of megahertz

  the period of investigation ("summer 2024" or similar) should not appear in the main body of a peer-reviewed scientific article, especially in the introduction or abstract.You can replace with "A GPR survey was conducted in 2024...;The investigation took place between May and July 2024..."Fieldwork was carried out in mid-2024...

Comments on the Quality of English Language

The English throughout the manuscript is mostly understandable, but there are several areas where the language could be improved to make the text clearer and more fluid. In particular, some sentences are too long or awkwardly phrased, especially in the introduction and discussion sections. 

Author Response

Thank you for taking the time to review this manuscript. Please see the detailed responses attached. 

Author Response File: Author Response.pdf