Articles | Volume 4, issue 2
© Author(s) 2022. This work is distributed underthe Creative Commons Attribution 4.0 License.
Technical note: Evaluating a geographical information system (GIS)-based approach for determining topographic shielding factors in cosmic-ray exposure dating
- Final revised paper (published on 14 Dec 2022)
- Supplement to the final revised paper
- Preprint (discussion started on 03 Aug 2022)
- Supplement to the preprint
Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor |
: Report abuse
RC1: 'Comment on gchron-2022-18', Yingkui Li, 19 Aug 2022
- AC1: 'Reply on RC1', Felix Martin Hofmann, 25 Oct 2022
RC2: 'Comment on gchron-2022-18', Michal Ben-Israel, 22 Sep 2022
- AC2: 'Reply on RC2', Felix Martin Hofmann, 25 Oct 2022
Peer review completion
AR: Author's response | RR: Referee report | ED: Editor decision
ED: Publish subject to minor revisions (further review by editor) (08 Nov 2022) by Greg Balco
AR by Felix Martin Hofmann on behalf of the Authors (14 Nov 2022)  Author's response Author's tracked changes Manuscript
ED: Publish as is (23 Nov 2022) by Greg Balco
ED: Publish as is (24 Nov 2022) by Georgina King(Editor)
This manuscript conducted a comprehensive validation of a GIS toolbox in determining topographic shielding factors for cosmogenic surface exposure dating based on >77 field-measured data in three topographic settings. The manuscript also compared the results from different DEM types and resolutions. This validation confirmed the initial argument of Li (2018) that the derived topographic shielding factors are relatively consistent with different DEM resolutions. Therefore, it is recommended using a medium resolution DEM to derive topographic shielding to speed up the computation and avoid the impact of small topographic barriers. The validation also suggested the use of vegetation-corrected DEMs for the calculation because the vegetation may affect the skyline analysis and derived incorrect shielding factors. For different DEM types, the manuscript validated the use of SRTM 30-m DEM in determining topographic shielding factors because of its wide availability and the consistency with field-measured data. Overall, this manuscript provides a useful validation of the GIS-based approach and an insightful guidance in selecting suitable DEM data for the determination of topographic shielding factors.
The following are some of my comments and suggestions for the author to improve the manuscript:
Page 5: The model represented by ArcGIS modelbuilder in Figure 1 is necessary. Sure, the users can run the tool of Li (2018) in this way in modelbuilder, but the simplest way to run the analysis is by double clicking the tool and specify the inputs in the GUI of this tool. In this figure, I suggest the author to show a screen shot of the GUI (panel A on the left) and then the screen shot of the attribute table of the point file (panel B on the right) to show how the optional parameters, such as dip, slope, and height, are organized. In addition, this tool accepts both shapefile and feature class as the input of the sample sites. The author may just use a GIS point file of the sampling sites (vector) here.
Page 17: Figure 6: May be better to also show the correlations between the shielding factors derived from 1 m DEM and resampled 12m and 30 m DEMs to see if there are major changes on the shielding factors because of the changes in DEM resolutions.
Page 18: Figure 7: Why the number reduced to 23 in this figure? The number is 37 in the previous figures. If the reason is because only having 23 CRE ages, the author can just report the panel (c) because the previous figures already show strong correlations between GIS and field-derived values.
Page 20: Figure 9 and the texts: It will be great to discuss the correlations after removing the "outlier" (STEI-7)? I guess the field measurement for this sample site may be problematic.
Pages 21-25: Section 4.2: Sensitivity tests. The three sensitivity experiments reported in this section are the results from the three study sites. They are apparently different from the three sensitivity tests described in the method section (Page 13). Based on the descriptions in the method section, the first test is to assess the effect of the different methods for calculating topographic shielding factors on CRE ages of boulders in mountains with an intermediate elevation that have been exposed to cosmic radiation since the Late Pleistocene. The second test is to determine whether the choice of topographic shielding factors has a significant impact on the CRE ages of surfaces that have been exposed for the last few millennia. The third test is to assess the impact of topographic shielding factors on the young CRE ages of LIA or younger. Although the three tests are related to the three sites, respectively. They have different focuses. I hope the author can check the consistency of the three sensitivity tests described in the method and results sections.
Tables 2, 3, and 4 are likely not necessary for the main text. Maybe can put these tables as the supplementary. The author can create the histograms of the CRE age difference for the three sites and put them in one figure. In this way, the main text can be shortened.
Pages 26-29: Section 5.1: The discussion about the vegetation-corrected or not corrected should belong to Section 5.3. There are some repeated parts in these sections. The author needs to re-organize the writing to avoid the repeated sentences and paragraphs.
It is interesting that the vegetation seems have different impacts on SRTM DEM and TanDEM-X. This can be a good point. SRTM data is collected in February 2000 (leaf off season), so that the impact of vegetation cover on topography may be not very high. When the TanDEM-X data were collected? if it was during the grown season, it may have a bigger impact. I suggest the author to check the data sources of different DEM sources and explain the vegetation impact on topography more.
In the discussion and conclusions, the author argues that a relatively low-resolution DEM is better for determining the topographic shielding factors. I suggest the author using medium resolution instead. A low-resolution DEM, such as SRTM 90-m DEM, is not very accurate for the topographic shielding factors as illustrated in Figure 2 (Page 7).
The manuscript is relatively long and there are some repeated sentences and paragraphs or meanings in different sections. I suggest the authors to re-organize the writing to make the manuscript more concise.
I also have some detailed comments on the Pdf version of the manuscript. Hope my comments and suggestions will be helpful for the improvement of this manuscript.