Monitoring Land Subsidence Using PS-InSAR Technique in Rawalpindi and Islamabad, Pakistan

Round 1

Reviewer 1 Report

Comments on the paper “Monitoring Land Subsidence Using PS-InSAR Technique in Rawalpindi and Islamabad, Pakistan” by Khan et al.

 

This paper illustrates an important case history of ground subsidence phenomena occurred in an urban settlement of Pakistan. The vertical displacements are quite relevant, amounting to approximately 20 cm in 30 months, causing some damage to buildings. This deformation episode is well documented by Sentinel 1 synthetic aperture radar measurements, by using the PS-In SAR method and a classic standard software.

This paper is generally well written, and the topic is suitable for Remote Sensing. The authors relate this subsidence phenomenon to the rise of population and the change in the ground level. They also relate to subsidence to the number of tube wells. These last considerations are however only qualitatively illustrated and discussed; I have found this part of the manuscript is presented in an unsatisfactory way. The geological arguments are also insufficiently documented: the references to the seismic activity are also not clear. 

I have generally found that this paper looks like more to a technical report than a scientific paper and there is any attempt to quantitative and scientifically sound demonstration of the basic arguments presented. I believe a substantial revision should be made for making acceptable it for a scientific Journal.  

Author Response

Thank you so much for your valuable comments. 

Responses are attached in the file below.

Author Response File: Author Response.pdf

Reviewer 2 Report

This research explored the utility of persistent scatterer interferometry synthetic aperture radar (PS-InSAR) approach with Sentinel-1 synthetic aperture radar (SAR) imagery to track land subsidence in the Rawalpindi area located at the northern edge of the Potwar Plateau in Pakistan. As part of the methodology, the SARPROZ software was used to study a series of Sentinel-1 imagery obtained from January 2019 to June 2021. Results showed that the proposed approach can effectively map, detect, and monitor subsidence-prone terrain regions. The reviewer believes that the current version of the manuscript is not yet ready for publication; the authors are encouraged to consider the following comments and suggestions and revise the manuscript accordingly.

1. The authors should consider streamlining the Abstract section. Currently, the Abstract section is not in a natural flow and it provides a lot of information. The authors should make it more concise. In addition, the authors should expand the Introduction section. The authors should introduce more background about this research. The authors should also split the Introduction section into two sections, including an Introduction section and a Background (or Related Work) section. The introduction section should focus on introducing the research objectives and research questions, while the Background section should focus on literature review of related work and defining research gaps.

2. The authors should include more information about the SARPROZ software. This will help other researchers who want to replicate the research. In addition, the authors should provide a supplement file which includes all parameter settings for using SARPROZ to process images. The authors should also include appropriate citations for each of the used parameter values.

3. The reviewer still does not fully understand the image processing steps. The authors provided information about the data being used for this study, however, they did not provide any descriptive information about image processing.

4. Using a software to process images to get results did not qualify for an explorative research. The authors need to improve the manuscript to make it focus on research. For example, the paper should perform sensitive analysis to examine the most appropriate parameter values for the software or the study area. Additionally, the authors could using different input data to select the more appropriate input image dataset. Either way, the manuscript needs a major revision.

5. In the conclusion section, the authors need to provide more discussion on future research topics. For example, the authors should consider using unmanned aircraft systems with InSAR imaging capabilities to evaluate subsidence. The authors need to review the paper of “The Impact of Small Unmanned Airborne Platforms on Passive Optical Remote Sensing: A Conceptual Perspective”.

 

6. All of the figures need to be improved. A lot of the figures are not legible to read, especially Figure 7 to 10. If at all possible, please create vector images for readability. 

 

Author Response

Thank you so much for your valuable comments. 

Responses are attached in the file below.

Author Response File: Author Response.pdf

Reviewer 3 Report

It is very important and good theme for research in practical use. However, I have a several comments and question as follows:

 

(1)  In chapter 2.2, it is not good to list up several soil types as subchapter of Ch. 2.2 and difficult to understand the relationship with Figure 3.

(2)  In figure 4 is data processing steps in your proposed research Method, but it is difficult for me to understand what advantage or research method is only using figure 4. You should break down your data processing steps in subchapter and explain what new and advanced method is in this study clearly. Looks like, you only follow legacy research processing steps.

(3)  In figure 5, are those ASI for descending and ascending? With figure 4, I could not understand why you have two ASIs.

(4)  What is an impact of vegetation condition change when you choose PS INSAR data? Since C-band can not be penetrated in high vegetated area and timing, you have to select data carefully.

(5)  You mention about the relationship between soil type and subsidence area in the beginning and conclusion but there are no clear information about that including figure 11. Do you select PS points based on soil type or Land usage?

(6)  In figure 14, you mention the location of tube wells and subsidence. But, the relationship is not clearly mentioned and cracks house location are also not mentioned in the figure.  

Author Response

Thank you so much for your valuable comments. 

Responses are attached in the file below.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I agree with the present version of the manuscript, which has been improved according to my previous comments.

Author Response

I agree with the present version of the manuscript, which has been improved according to my previous comments.

Reviewer 2 Report

The authors have addressed all my comments. 

Author Response

The authors have addressed all my comments.

Reviewer 3 Report

PSI, PS-InSAR and PSI technology, you should have consistency.

Line 120, PSI should be PS-InSAR.

Line 222, PSI technology should be PS-InSAR technology

Line 267, PS is spell out at the first time. But, it should be spell out more earlier. persistent scatterers (PS),

Author Response

PSI, PS-InSAR and PSI technology, you should have consistency.

Response: Thank you so much for your valuable comments and for pointing this out. As per your suggestions, PSI has been changed to PS-InSAR; please check the yellow highlighted spots in the manuscript.

Line 120, PSI should be PS-InSAR.

Response: Thank you for your kind suggestion. We have changed according to your suggestion. Please check.

Line 222, PSI technology should be PS-InSAR technology

Response: Thank you for your kind feedback. PSI has been changed to PS-InSAR. Please check.

Line 267, PS is spell out at the first time. But, it should be spell out more earlier. persistent scatterers (PS),

Response: Thank you so much for pointing this out. As per your suggestions, we have removed “persistent scatterers” from line 267. It has already been discussed with the abbreviation above in the abstract and introduction section. Please check.