Integrating Remote Sensing and GIS-Based Map Analysis in Determining Spread of Built-Ups and Land-Use Dynamics of Terrain of Onitsha Metropolis, Anambra State, Nigeria

Comments 2: [2) Page 5, line 169. I believe you used Landsat 8, Landsat 7 and Landsat 4-5 NOT only Landsat 8.]

Response 2: Agree. I/We have, accordingly, done/revised/changed/modified…..to emphasize this point. We have included the omissions which were made because we were trying to present these ideas in a minimized manuscript. – page numbers 6 and 7]

“[The satellite images were sourced from the United States Geologic Survey (USGS) archive (Shuttle Radar Topographic Mission (SRTM) and Landsat 4-5 TM, 7 ETM, and 8 OLI-TIRS) (Table 1). The geology and geomorphological variables extracted from the satellite images data (Shuttle Radar Topographic Mission (SRTM)) were processed using ArcGIS 10.2. Land Use Land Cover Change (LULCC) of Onitsha Metropolis was analyzed with much emphasis on built-up areas (Appendix A). Landsat 4-5 TM, 7 ETM, and 8 OLI-TIRS satellite images data of the area sourced from USGS were processed using ArcGIS 10.2, for the period of forty (40) years from 1982 to 2022, with intervals of ten (10) yethis study, out of the nine (9) bands; bands 4, 3, 2 were chosen for land use analysis. Some of the stages in data processing and analyses that were employed in the study include Layer stacking of bands 4, 3, 2, and 5, 4, 3 of the TM, ETM, and OLI Landsat satellite images respectively, Radiometric and Geometric Correction using ERDAS Imagine 9.2 to correct the haze distortion where necessary and image sharpening to enhance the appearance of the images.]”

Comments 3: [3) Page 5, line 173. What classification method did you use? You have to explain it and report the classification accuracies.]

Response 3: [We have responded to this observation. – page numbers 6 and 7]. Thank you for pointing this out. I/We agree with this comment. Therefore, I/we have included “[For the purpose of this study, out of the nine (9) bands; bands 4, 3, 2 were chosen for land use analysis. Some of the stages in data processing and analyses that were employed in the study include Layer stacking of bands 4, 3, 2, and 5, 4, 3 of the TM, ETM, and OLI Landsat satellite images respectively, Radiometric and Geometric Correction using ERDAS Imagine 9.2 to correct the haze distortion where necessary and image sharpening to enhance the appearance of the images. Image extraction of the shape file of the study area was done by masking in ArcGIS 10.2, while the accuracy assessment and ground truth verifications were also carried out.

Two different coordinate systems were used in the GIS analysis of this study. The World Geodetic System 1984 (WGS 1984) for the large map (Anambra State), and Universal Transverse Mercator (NGN UTM Zone 39N) for the small map (Onitsha Metropolis).]”

Comments 4: [4) Page 14, Discussion, line 310. Discuss the limitation of your method and draw future directions.]

Response 4: There were no specific limitations in this study, except for finance which is a general problem in research and the fact that the output of any GIS analysis is a reflection of the input and does not represent 100% of phenomena on ground but serves as models.  According to George Box, ‘All models are wrong but some are useful”.

4. Response to Comments on the Quality of English Language

Point 1:

Response 1:    (The quality of English language is appreciable, however, some updates were made for improvement and clarity)

5. Additional clarifications

[The intention of the authors is to produce these ideas in a manuscript that is as short as possible. Some reviewers distaste reviewing long manuscripts].

Comments 1: [The introduction needs further improvement. The introduction lacks reference value, and it fails to fully demonstrate the researcher's comprehensive understanding of the field and the identification of research gaps. The study lacks a more comprehensive review of the existing relevant studies, and suggests further refining the research review to clarify the research gap of the existing studies, so as to reflect the value and innovation of the research]

Response 1: [We have added and discussed some previous works in the Introduction] Thank you for pointing this out. I/We agree with this comment. Therefore, I/we have added [There are so many studies carried out in Onitsha Metropolis and environs. Nkiruka et al (2023) looked at the land use land cover change of the Metropolis with focus on their effects on flooding; Ezeomedo and Igbokwe (2013) studied the land use land cover change of Onitsha urban and environs to establish the pattern, extent, and magnitude of change from 1964 to 2008.  Akinbobola (2019) simulated the land use change from 1986 to 2016 with emphasis on land surface temperature (LST), and predicted the possible outcome of the land use change spread in 2030 and 2044. Ifeka and Akinbobola (2015) in their study in some selected stations in Anambra State of which Onitsha Metropolis was among, established that there is land use change variations in Onitsha Metropolis and other selected stations from 1986 to 2013. Onwuka et al (2017) modeled the land use cover change of Onitsha Metropolis for 1986 to 2016 and made a prediction of possible scenario of the land use land cover change of Onitsha Metropolis in 2031 and the consequent negative effects of environmental problems associated with unplanned and congested built ups……... In addition, the study intends to establish and quantify the extent of encroachment of built up on areas of the geologic formation that are not suitable for building constructions.– page 3]

Comments 2: [As can be seen from the title, the focus of this study should be the dynamic distribution of built-up and land use. However, in the main text, the research content is mainly the geology and land use land cover change, which does not highlight the importance of this study on “built-up”. This shows that the subject and content of the study are inconsistent.]

Response 2: The subject and content of this study are the same. Land use types are determined based on geological formations. Different geology supports different land use types. We looked at the spread of built up part of land use that has encroached on other land uses as it increase, shrinking other land uses in the space under study and also into the geologic formation not suitable for building constructions (built up).] 

Comments 3: [The depth of the discussion needs to be further enhanced. This study did not make further comparative analysis of the methods, data and results of related research with this study, which makes it difficult to highlight the innovation points and research contributions of this study.]

Response 3: [We have responded to this observation. – page number 16]. Thank you for pointing this out. I/We agree with this comment. Therefore, I/we have updated. “[These findings agree with that of some researchers’ findings. The analysis result of the study conducted by Nkiruka et al (2023) revealed that built up increased by 9.4% from 2008 to 2013 and another 5.5% increase from 2013 to 2018, while there was a drastic reduction in the percentage of vegetation cover under the same period in Onitsha North and South Local Government Areas. Akinbobola (2019) who recorded 74.25% for vegetation, 22.31% for built up, and 2.45% for water bodies in 1986. In 2002, vegetation was 69.80%, built up was 27.56%, and water body was 2.65%, while in 2016, the vegetation was 64.39%, built up was 33.26%, and water body was 2.35%. Ifeka and Akinbobola (2015) recorded vegetation to be 26%, built up to be 45%, and water body was 5% in 1986. In 2000, vegetation was 28%, built up was 57%, and water body was 7%, while in 2013, vegetation was 32%, built up was 61%, and water body remained 7%. Onwuka et al (2015) land use cover classification analyses showed that vegetation in 1986 was 79.43% in 1986, 65.64% in 2001, and 62.61% in 2016 respectively. Ezeomedo and Igbokwe (2013) calculate the LULCC of Onitsha Metroplolis to 51.78% for vegetation, 41.64% for built up, and 5.84% for water body in 2005. In 2008, vegetation was 18.74%, built up was 59.50%, while water body was 2.88%. There is a general concurrence in the sense that built up has been increasing and spreading into other land uses thereby shrinking the space for them. It is very clear that from other studies finding that vegetation was decreasing rapidly and built up increasing in its stead even though the rate varies.]”

Comments 4: [Normative issues expressed in the chart: the small picture in the upper right corner of Figure 1 should not cover up the larger picture below, and the two pictures should not share the same warp and weft scale. The yellow bottom picture on the right in Figure 2 lacks a legend. Figure 5-9 has the same problem, that is, the range indicated by the black box in the left figure is different from that in the right figure.]

Response 4: [We have responded to this observation. – Figures 1, 3, 4, 6 – 10, 12 - 16]. Thank you for pointing this out. I/We agree with some of this comment. Therefore, I/we have updated the figures concerned. [The range indicated with the black box on the inset map of Anambra State is the same with the map of Onitsha Metropolis. The difference in orientation is because of differences in coordinate system.] “[Two different coordinate systems were used in the GIS analysis of this study. The World Geodetic System 1984 (WGS 1984) for the large map (Anambra State), and Universal Transverse Mercator (NGN UTM Zone 39N) for the small map (Onitsha Metropolis).]”. [There are no legends on all inset maps in the study because they are not the point of focus; they are used to show the location of the study area (Onitsha Metropolis) in a larger Anambra State map.]

4. Response to Comments on the Quality of English Language

Point 1:

Response 1:    (The quality of English language is appreciable, however, some updates were made for improvement and clarity)

5. Additional clarifications

[The authors intend to produce these ideas in a manuscript that is as short as possible. Some reviewers distaste reviewing long manuscripts].

Comments 1: [Introduce the reader to the methodology for extracting geology and geomorphology maps, based on SRTM.]

Response 1: [We have added and discussed more on the methodology] Thank you for pointing this out. I/We agree with this comment. Therefore, I/we have added [Diagrammatical Flowchart Representing the GIS Analysis Methods for the Geomorphological and LULCC Maps. – page 19]

Comments 2: [Landsat 8 began its mission on May 30, 2013. In other words, it is impossible to have used images from the OLI sensor (LANDSAT 8) before 2013. List which sensors from the LANDSAT series were used.]

Response 2: Agree. I/We have, accordingly, done/revised/changed/modified…..to emphasize this point. We have included the omissions which were made because we were trying to present these ideas in a minimized manuscript. – page numbers 6 and 7]

“[The satellite images were sourced from the United States Geologic Survey (USGS) archive (Shuttle Radar Topographic Mission (SRTM) and Landsat 4-5 TM, 7 ETM, and 8 OLI-TIRS) (Table 1). The geology and geomorphological variables extracted from the satellite images data (Shuttle Radar Topographic Mission (SRTM)) were processed using ArcGIS 10.2. Land Use Land Cover Change (LULCC) of Onitsha Metropolis was analyzed with much emphasis on built-up areas (Appendix A). Landsat 4-5 TM, 7 ETM, and 8 OLI-TIRS satellite images data of the area sourced from USGS were processed using ArcGIS 10.2, for the period of forty (40) years from 1982 to 2022, with intervals of ten (10) years. For the purpose of this study, out of the nine (9) bands; bands 4, 3, 2 were chosen for land use analysis. Some of the stages in data processing and analyses that were employed in the study include Layer stacking of bands 4, 3, 2, and 5, 4, 3 of the TM, ETM, and OLI Landsat satellite images respectively, Radiometric and Geometric Correction using ERDAS Imagine 9.2 to correct the haze distortion where necessary and image sharpening to enhance the appearance of the images.]”

Comments 3: [In figures 11 to 15 it is difficult to visualize the geological classes.]

Response 3: [We have responded to this observation. – Figures 1, 3, 4, 6 – 10, 12 - 16]. Thank you for pointing this out. I/We agree with this comment. Therefore, I/we have updated them.

Comments 4: [There is no figure on the geomorphological map.]

Response 4: [We have responded to this observation. – the geomorphological map has been corrected]. Thank you for pointing this out. I/We agree with this comment. Therefore, I/we have corrected it.

4. Response to Comments on the Quality of English Language

Point 1:

Response 1:    (The quality of English language is appreciable, however, some updates were made for improvement and clarity)

5. Additional clarifications

[The intention of the authors is to produce these ideas in a manuscript that is as short as possible. Some reviewers distaste reviewing long manuscripts].

Comments 1: [To improve the work, theoretical background and reference list should be expanded. Details about conducted interviews should be provided. There are several pages that contains only maps from various periods. To provide clarity, these maps should be reorganized in some groups and provide comparative analysis and explanation, along the maps. Also, there is no need to repeat the same legend, which only takes space. Instead, original maps can be provided in Appendix. Recommendations that arose from the results should be discussed in the Discussion Section, while Conclusion only provides an overview of the work carried out and recommendations and future work in general.]

Response 1: [We have added and discussed more on the introduction, methodology, and have expanded the reference list. The authors intended the maps to stand alone, while comparisons were made on the chart that follows after the maps] Thank you for pointing this out.

Comments 2: [There are some typos that needs to be corrected]

Response 2: [We have responded to this observation. – corrected]. Thank you for pointing this out. I/We agree with this comment. Therefore, I/we have corrected it.

Comments 3: [References should be numbered.]

Response 3: [We are of the opinion that the structure of the reference list will be determined by the editors]. Thank you for pointing this out.

4. Response to Comments on the Quality of English Language

Point 1:

Response 1:    (The quality of English language is appreciable, however, some updates were made for improvement and clarity)

5. Additional clarifications

[The intention of the authors is to produce these ideas in a manuscript that is as short as possible. Some reviewers distaste reviewing long manuscripts].

Comments 1: [1) Page 7, Table 1. Each type of Landsat sensors should be presented in one row, the date must be different for each (row) Landsat data (1982, 1992, 2002, 2012 and 2022).]

Response 1: [The date on ‘Table 1’ is the date of data acquisition (the date the satellite images were downloaded), and not the capture date by the Satellite] Thank you for pointing this out. I/We agree with this comment. Therefore, I/we have made clarifications [We want to present the contents of this study as brief as we can. The information on Table 1 is enough in addressing the issue of data source, type, and date]

Comments 2: [2) Page 7, line 248, Results. You have to report the error matrix in a table: overall accuracy, kappa statistic, user’s accuracy and producer’s accuracy.]

Response 2: Agree. I/We have, accordingly, done/revised/changed/modified…..to emphasize this point. It is not possible to give every detaiedl information in this study from the introduction to the conclusion without repeating things that could be presented in a summary

Comments 3: [3) I believe the Landsat data that acquired in 2012 is affected by the “Scanline Error”. How did you deal with this issue?]

Response 3: [Errors are most considered when they varied or skew the results]. Thank you for pointing this out. I/We agree with this comment. Therefore, I/we used Google Earth Pro “[We use Google Earth Pro to confirm and validate all the land use classes during ‘Training Sampling’.]”

Comments 4: [4) Think about the limitations in terms of the data and algorithm that you utilized. For example, the spatial resolution of Landsat data (30 m) is one limitation because there are other satellite data with finer spatial resolutions and may improve the results. I know the finer spatial resolution data are not available in 1982 and 1992 but you can mention it (the spatial resolution) as a limitation. In addition, the MLC which is a hard-pixel-based approach could be a limitation because a soft-pixel-based approach such as the support vector machine (SVM) or the object-based approach may improve your results.]

Response 4: Thank you for pointing this out. I/We agree with this comment. We see the comments number 4 as a suggestion which would have be taken into consideration if the study is about comparative analysis of different Satellite image data or sources. However, the reviewer has pointed out what seemed like a gap in the study which we may not want to go into at this stage because doing so will mean starting the study afresh or total overhaul of the data sources and acquisition. Research is a continuum; no researcher can articulate everything conceptualized in one study.Others can conduct this same study using different data sources and method of analysis to either arrive at the same result or otherwise.

4. Response to Comments on the Quality of English Language

Point 1:

Response 1:    (The quality of English language is appreciable, however, some updates were made for improvement and clarity)

5. Additional clarifications

[The intention of the authors is to produce these ideas in a manuscript that is as short as possible. Some reviewers distaste reviewing long manuscripts].

Comments 1: [The quality of the revised paper has been greatly improved, and it is recommended to accept.]

Response 1: [Thank you for your kind comments] Thank you.

Comments 1: [The quality of the revised paper has been greatly improved, and it is recommended to accept.]

Response 1: [Thank you for your kind comments] Thank you.