Spectral Unmixing for Mapping a Hydrothermal Field in a Volcanic Environment Applied on ASTER, Landsat-8/OLI, and Sentinel-2 MSI Satellite Multispectral Data: The Nisyros (Greece) Case Study

Round 1

Reviewer 1 Report

This paper is very clearly written, very well structured and the reader is well guided to understand the methodology. The final comparison of the determination of the altered zones by both the SU and the index calculation is convincing.  The result therefore deserves to be published; I therefore recommend the publication after minor changes.

Main points / comments :

• Regarding the geometrical perspective of SU: Have you checked if the vectors (spectral signatures) are independent? (this is necessary to project in their base)
• I think that you could have scanned and classified the map presented in Fig. 7 (g) to really quantify (and not only compare visually) the correspondence of the altered zones between the terrain map, the SU method and the index calculation.
• Note the index calculation gave a less contrasted classification and incorrectly indicate some alteration outside the zone, this is a point to be highlighted.
• Have you been on the field to validate the ROI choice? In terms of eventual subpixel mixing of different endmembers.
• Are there any effects of solar exposition (talus for instance) ?

Minor points:

238 : instead of left, prefer lower wavelength

438 : Remove “: they”

Jean Vandemeulebrouck,

Institut des Sciences de la Terre, Grenoble, France.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Please see the attached comments.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

This manuscript is much improved and I thank the authors for their attention to my comments and suggestions.  I recommend that the revised manuscript be accepted for publication.