Uncertainties and Perspectives on Forest Height Estimates by Sentinel-1 Interferometry
Round 1
Reviewer 1 Report
I reviewed the revised manuscript and found that my suggestions have been improved. I have no further comment for authors and I am pleased to recommend this manuscript for publication in this journal.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
I thank the authors for their responses to earlier review comments.
English or grammar questions:
Abstract:
Line 9-11: Should this sentence be? (I have modified a few words): “SAR interferometry (InSAR) techniques have been extensively adopted to retrieve digital elevation models (DEM) giving a representation of the continuous variation of Earth’ topography, including forests.”
If so, then line 11: “Unfortunately, InSAR has been proven to fail over vegetation…”
Line 12, Is “algorithms” the same as “techniques” in line 9? Or do the authors see this as one technique, and a number of algorithms are used for this technique?
Line 13: Please delete “very” ; otherwise it would be important to discuss whether that means significant as in statistically significant.
Line 14: “…a sensitivity analysis was performed with the aim of properly set up the involved operational parameters…” Perhaps this should read “…a sensitivity analysis was performed with the aim of properly initializing the relevant operational parameters…” ?
L16-17: “..proposed concerning the adoption of the resulting..” , does this mean “…proposed to test the resulting “optimal values”...” ?
Line 19-20: The sentence beginning “With the aim of supporting the operational transfer of our deductions…”, does it mean “All our analyses were conducted using data and observations from the Copernicus Sentinel-1 mission, so that our results could be easily adopted for use with output from that mission.” ?
Line 36, replace “ones” with “surveys”.
L37-39: consider “…well-fit forest requirements of making it possible to map and monitor wide areas and allowing a near-early change detection and..”
L39-41: consider “Synthetic aperture radar (SAR) is known to be useful for estimating forest geometric features, because data can be recorded in all-weather conditions including equatorial/tropical areas often covered by clouds.”
L42-44: Consider “Among SAR application and methods, SAR interferometry (InSAR) techniques have been extensively adopted to generate digital elevation models (DEM), that are intended to provide a continuous representation of Earth topography, including forested areas.”
L47-49: Consider-- “An ordinary InSAR processing workflow relies on a phase unwrapping step aimed at unambiguously recovering the local topography, which is generally achieved by unitarily processing the entire scene.”
L49-51: Consider – “This approach has proven to consistently fail over vegetation where signal coherence values are low. Ordinary algorithms tend to omit these areas during unwrapping [15,16], so that InSAR-derived DEMs over areas of vegetation are highly unreliable [17].” However, I am not sure what the cause and effect is so that may not be a correct sentence either. Perhaps the sentence is more accurate this way: “ Ordinary algorithms tend to omit areas of vegetation during unwrapping phase [15,16], so the approach has proven to consistently fail where signal coherence values are low. This makes InSAR-derived DEMs over areas of vegetation highly unreliable [17].”
L55: insert the word “by” in the sentence so it reads “..data by avoiding phase…”.
L55-58: maybe what is meant is the following: “This method changes the working paradigm from a mapping problem involving the entire scene, to a local paradigm based on the comparison between a forest pixel interferogram and a reference one closely located outside the forest.”
L60-62: Consider “….a sensitivity analysis was also performed with the aim of properly initializing the relevant operational parameters (i.e. baseline and multilooking factors) to maximize…”
L104: use categories not category.
L105: insert an “and”-- so “.. and (c) Interferometric… “
L107: Consider “Approach (b) is mainly applied…” NOTE: here the word approach is used, whereas on page one terms such as techniques and algorithms were used. Please be consistent with what is being called an approach, what is a technique, and what is an algorithm.
L110-111: Consider “Approach (c) appears to be the most promising, because it is somewhat consistent with technical features of S1 data.”
L147: remove extra period.
I stopped by line 114, though I did notice the item in line 147.
Please go through the rest of the manuscript and write with care.
Also, it is still not clear whether this is an application of a technique from the cited IEEE transactions, or if this manuscript is describing a totally new approach. Please add text to make this clear.
Thank you.
I thank the authors for their responses to earlier review comments.
English or grammar questions:
Abstract:
Line 9-11: Should this sentence be? (I have modified a few words): “SAR interferometry (InSAR) techniques have been extensively adopted to retrieve digital elevation models (DEM) giving a representation of the continuous variation of Earth’ topography, including forests.”
If so, then line 11: “Unfortunately, InSAR has been proven to fail over vegetation…”
Line 12, Is “algorithms” the same as “techniques” in line 9? Or do the authors see this as one technique, and a number of algorithms are used for this technique?
Line 13: Please delete “very” ; otherwise it would be important to discuss whether that means significant as in statistically significant.
Line 14: “…a sensitivity analysis was performed with the aim of properly set up the involved operational parameters…” Perhaps this should read “…a sensitivity analysis was performed with the aim of properly initializing the relevant operational parameters…” ?
L16-17: “..proposed concerning the adoption of the resulting..” , does this mean “…proposed to test the resulting “optimal values”...” ?
Line 19-20: The sentence beginning “With the aim of supporting the operational transfer of our deductions…”, does it mean “All our analyses were conducted using data and observations from the Copernicus Sentinel-1 mission, so that our results could be easily adopted for use with output from that mission.” ?
Line 36, replace “ones” with “surveys”.
L37-39: consider “…well-fit forest requirements of making it possible to map and monitor wide areas and allowing a near-early change detection and..”
L39-41: consider “Synthetic aperture radar (SAR) is known to be useful for estimating forest geometric features, because data can be recorded in all-weather conditions including equatorial/tropical areas often covered by clouds.”
L42-44: Consider “Among SAR application and methods, SAR interferometry (InSAR) techniques have been extensively adopted to generate digital elevation models (DEM), that are intended to provide a continuous representation of Earth topography, including forested areas.”
L47-49: Consider-- “An ordinary InSAR processing workflow relies on a phase unwrapping step aimed at unambiguously recovering the local topography, which is generally achieved by unitarily processing the entire scene.”
L49-51: Consider – “This approach has proven to consistently fail over vegetation where signal coherence values are low. Ordinary algorithms tend to omit these areas during unwrapping [15,16], so that InSAR-derived DEMs over areas of vegetation are highly unreliable [17].” However, I am not sure what the cause and effect is so that may not be a correct sentence either. Perhaps the sentence is more accurate this way: “ Ordinary algorithms tend to omit areas of vegetation during unwrapping phase [15,16], so the approach has proven to consistently fail where signal coherence values are low. This makes InSAR-derived DEMs over areas of vegetation highly unreliable [17].”
L55: insert the word “by” in the sentence so it reads “..data by avoiding phase…”.
L55-58: maybe what is meant is the following: “This method changes the working paradigm from a mapping problem involving the entire scene, to a local paradigm based on the comparison between a forest pixel interferogram and a reference one closely located outside the forest.”
L60-62: Consider “….a sensitivity analysis was also performed with the aim of properly initializing the relevant operational parameters (i.e. baseline and multilooking factors) to maximize…”
L104: use categories not category.
L105: insert an “and”-- so “.. and (c) Interferometric… “
L107: Consider “Approach (b) is mainly applied…” NOTE: here the word approach is used, whereas on page one terms such as techniques and algorithms were used. Please be consistent with what is being called an approach, what is a technique, and what is an algorithm.
L110-111: Consider “Approach (c) appears to be the most promising, because it is somewhat consistent with technical features of S1 data.”
L147: remove extra period.
I stopped by line 114, though I did notice the item in line 147.
Please go through the rest of the manuscript and write with care.
Also, it is still not clear whether this is an application of a technique from the cited IEEE transactions, or if this manuscript is describing a totally new approach. Please add text to make this clear.
Thank you.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
Regarding Figure 1, I meant there were no explanations on used variables. Like abbreviations are spelled out when they appear the first time, variables should be defined where they are used the first time in a manuscript. “See section,,,” is not acceptable in this case. Likewise, L60-67 needs to be revised.
> Authors: hv is the expected average forest volume depth, while dh is the estimated forest height by the proposed approach. The first is suppose known by existing auxiliary information or by user assumption according to local forest stand features, while the second one resulted from proposed model application.
I asked where this explanation appeared in the manuscript.
> Authors: In Figure 5a hv is the expected average forest volume depth as reported in eq. ? is the coherence, it was not mentioned in the figure 5 but in the figure 6. Since Figure 5b is strictly related to figure 5a it is authors opinion that a single image can make more readable this section.
I meant that I don’t get which is the figure (a) and which is the figure (b) explicitly. Or, the authors can describe it as Figure 5 (a), (b), and (c). Figure 5 (a) and Figure 6 seem the same.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
160-161: Consider: It is worth highlighting that this formula does not take care of ? uncertainty that has to be further considered to properly model error propagation….
224: Consider: Because ??ℎ?????,????????,????? are independent from any operational parameter that can…
241—242: Consider: These issues determine significant observational errors [50] making this approach with S1 data a poor choice. NOTE: the word deprecable is not used commonly.
L251-252: please rewrite.
L254: delete ‘deeply’.
L278: .. makes it possible….
L285-286: Consider: These cannot be directly accounted for, because they are difficult to model.
L291: use further not furtherly
L294: consider deleting “supposing to relate” (it does not make sense as written)
L300: change “to” to “with”
L309-311: consider: With reference to figure 2, one can deduce that a baseline value lower than about 120 m can be used with caution to ensure that forest height can be estimated. In fact, rarely do forests around the world show tree height greater than 100 m.
L361: use “Because” instead of “Being”
L376: consider: It is worth noting that ??ℎ values are certainly underestimated.
L379: minimize rather than minimizing
L382: It is worth noting that the optimal values…
L385-387: Consider: The operational utility of this model can be easily exemplified using a case study. Suppose we investigate tree heights in a forest with an expected value of 25 m. The model of figure 5b makes possible to calculate a resulting optimal baseline….
Note I have never seen the word paradigmatic used.
L396: …made it possible…
L403: delete the word “it”
L428-429: consider Otherwise, in the proposed approach similar accuracy was found which avoided phase unwrapping, resulting in a more robust and controllable forest height uncertainty estimation.
There are 5-6 more issues in sentences, please fix.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
